big tl;dr for a bigger post:
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To better understand how our decks behave in non-cEDH metas, we should consider the primary winning interactions along these three axii: interactability, conditionality, and respondability. Interactions that min-max all three are cEDH-quality, while interactions stronger in only one or two areas may be acceptable depending on the meta.
When I consider if an optimization fits within my meta, I consider three axii; interactability, conditionality, and respondability.
Interactability.
How easy or hard it is for players to stop that interaction from happening. Instant-speed windows of interaction are probably the first thing to come to mind, but overly tough board states also fall under this category. I've seen budget battlecruiser pods get wrecked by Sigarda, Host of Herons suited up with Darksteel Plate. Most of the time I don't bother trying to get rid of life from the loam because all it takes is some mana and cycle lands to dodge graveyard removal. The reason why craterhoof behemoth is so hated is because once that triggered ability goes on the stack, you have an instant-speed window to kill 15 tokens before they become 15/15 tramples, even if they do have to go through combat to kill you.
Conditionality.
What kind of conditions are needed for the interaction to be a game-winning one. It could be "get these two cards in your hand and the mana to cast them" (infinite combo), it could be "attack with this creature into a player with no available blockers and his life is less than the creature's power" (combat). I've seen salt from insurrection causing too many wins - in battlecruiser games there's no shortage of creatures hanging around the board, causing this to be a really easy condition to fill. It's also where you get the idea of people running combos but cutting all tutors, in effect, attempting to weaken the interactions by making them more conditional. Lots of stax strategies get more difficult to deal with if the conditions are just right.
Respondability.
While the line is a little blurry between this and interactability, the important factor here is time. How long it takes for a game-winning interaction to win the game. The "win out of nowhere" factor. A 2/2 bear takes 20 turns to kill a player. The defending player has 20 turns to find either an interaction with the bear (shock), or to break the winning condition (leave up a 2/2 blocker of your own). zurgo helmsmasher gives a player two untap phases to deal with, which seems fast, but zurgo is pretty interactable and conditional, and killing one player isn't going to win the game. Playing an aetherflux reservoir and passing the turn gives the table one untap phase each (so a total of 2 to 3?) to solve this problem, but could be more.
NOTE that I want to be very clear here, I'm not saying each one makes oppressive games, but rather it's a combination compared to metagame tolerance. Some players might get salty at progenitus putting them on a four-turn clock - that's could be from expecting higher interactability (can't remove it), higher conditionality (their blockers are useless), or too little respondability (four turns to find a solution is too fast). Other players might consider that situation laughably easy to solve, expecting low interactability (just counter it), low conditionality (tutor a solution), or high respondability (just kill the player).
Let's take a look at a simple compare/contrast with a couple of game-winning interactions:
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Situation A: cast planar portal, search up beacon of tomorrows, cast it, if the loop continues without interaction, you win.
Situation B: cast exsanguinate or torment of hailfire where x = lethal
One might be considered a breach of "no combo" agreements, while the other at worst would generate some salt at the table. Let's look at their similarities:
Interactability: Both interactions are hard to stop once the spell hits the stack. Aside from counter magic or some card that incidentally foils the plan, once a player gets to their main phase with mana intact and card in hand, there's not a whole lot that can be done about it.
Conditionality: They both either cost excessive amounts of mana. Many players may see that 20+ mana cost and think "if an opponent has that much mana, you've already lost anyways", but let's bear in mind that conditionality is incredibly meta dependent. Getting to 20+ mana is almost guaranteed on battlecruiser metas, for example, and the goal here is to understand metas, not to attach value judgements to them. Situation B is slightly less conditional, as you can potentially initiate the game-winning interaction on less mana if players are at lower life.
Respondability: Assuming the interaction is anticipated (reputation, revealed draws or tutors), the only recourse is player removal, mana denial, or stax. All options are generally frowned upon in battlecruiser-adjacent metas. That's even assuming the interaction can be anticipated; in all likelihood it'll come out of nowhere and give players an instant-speed window to prevent the interaction from bringing them out of the game.
All in all, both interactions are difficult to interact with, have easy conditions to table kill with, and are hard to mitigate.
Situation B: cast exsanguinate or torment of hailfire where x = lethal
One might be considered a breach of "no combo" agreements, while the other at worst would generate some salt at the table. Let's look at their similarities:
Interactability: Both interactions are hard to stop once the spell hits the stack. Aside from counter magic or some card that incidentally foils the plan, once a player gets to their main phase with mana intact and card in hand, there's not a whole lot that can be done about it.
Conditionality: They both either cost excessive amounts of mana. Many players may see that 20+ mana cost and think "if an opponent has that much mana, you've already lost anyways", but let's bear in mind that conditionality is incredibly meta dependent. Getting to 20+ mana is almost guaranteed on battlecruiser metas, for example, and the goal here is to understand metas, not to attach value judgements to them. Situation B is slightly less conditional, as you can potentially initiate the game-winning interaction on less mana if players are at lower life.
Respondability: Assuming the interaction is anticipated (reputation, revealed draws or tutors), the only recourse is player removal, mana denial, or stax. All options are generally frowned upon in battlecruiser-adjacent metas. That's even assuming the interaction can be anticipated; in all likelihood it'll come out of nowhere and give players an instant-speed window to prevent the interaction from bringing them out of the game.
All in all, both interactions are difficult to interact with, have easy conditions to table kill with, and are hard to mitigate.
Genesis wave for x = 15+
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interactability: Not very interactive on the stack. Once it resolves there is a lot of stuff on the table that can be reset with a board wipe, but there are very few cards that can tactfully reset the land advantage granted by this interaction.
Conditionality: Not very conditional, just get to a bunch of mana, and adhere to some simple deckbuilding restrictions (lots of permanents). Luck can play a factor, but even a bad dump can lead to a winning interaction much of the time.
Respondability: Maybe the players get one untap each to solve the board (assuming no haste or noncombat table kills were flipped), but certainly starting from the following turn the value snowball would create an insurmountable position equivalent to a table kill.
Conditionality: Not very conditional, just get to a bunch of mana, and adhere to some simple deckbuilding restrictions (lots of permanents). Luck can play a factor, but even a bad dump can lead to a winning interaction much of the time.
Respondability: Maybe the players get one untap each to solve the board (assuming no haste or noncombat table kills were flipped), but certainly starting from the following turn the value snowball would create an insurmountable position equivalent to a table kill.
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Interactability: Stack-only interaction most of the time
Conditionality: Caster needs to have a winning board state, opponents need to have a board state that can't keep up
Respondability: Meta-dependent, but if it is anticipated (so holding extra lands) in a meta filled with cheap removal, the winning board state can be dismantled before the win condition can secure the game. Remove the anticipation or the 1-cost removal though and there is very little that can be responded to, even if the win may take ten turns.
Conditionality: Caster needs to have a winning board state, opponents need to have a board state that can't keep up
Respondability: Meta-dependent, but if it is anticipated (so holding extra lands) in a meta filled with cheap removal, the winning board state can be dismantled before the win condition can secure the game. Remove the anticipation or the 1-cost removal though and there is very little that can be responded to, even if the win may take ten turns.
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Interactability: counter-only most of the time.
Conditionality: For symmetrical, caster needs to have a draw engine on board, for asymmetrical, the players getting hit only need to not have access to a draw engine. (though with how many draw engine commanders we have these days, this might be a bit tougher to achieve as a board state win)
Respondability: In the best conditions (secure a win in three or four turns against irrelevant boards), there's very little that can be done. In more general conditions, there's a lot of ways out.
Conditionality: For symmetrical, caster needs to have a draw engine on board, for asymmetrical, the players getting hit only need to not have access to a draw engine. (though with how many draw engine commanders we have these days, this might be a bit tougher to achieve as a board state win)
Respondability: In the best conditions (secure a win in three or four turns against irrelevant boards), there's very little that can be done. In more general conditions, there's a lot of ways out.
Anyways, I hope this could help people better understand what's going on when the table gets salty with a play that seems perfectly fine, or alternatively helps people understand why they personally get salty with different plays.