it seems like some people in this thread misunderstood what i meant when i talked about illusion being uncompetitive, so i'll go into it in more detail here.
first of all, let's get into the definition for uncompetitiveness from smogon's official tiering policy:
Uncompetitive - elements that reduce the effect of player choice / interaction on the end result to an extreme degree, such that "more skillful play" is almost always rendered irrelevant.
- This can be matchup related; think the determination that Baton Pass took the battling skill aspect out of the player's hands and made it overwhelmingly a team matchup issue, where even the best moves made each time by a standard team often were not enough.
- This can be external factors; think Endless Battle Clause, where the determining factor became internet connection over playing skill.
- This can be probability management issues; think OHKOs, evasion, or Moody, all of which turned the battle from emphasizing battling skill to emphasizing the result of the RNG more often than not.
now the first of these criteria doesn't really apply for illusion, because it isn't a matchup based thing more than anything else. for example, if you're using ho-oh as your mega diancie switchin, there's functionally no difference between dying to cb illusion mmx photon geyser and dying to head smash from mg diancie matchup-wise. this criterion could apply for some other things in the meta (if people can legitimately get x-1/x-0 records for suspects, there's likely an uncompetitive element in play), but i won't be getting into that here.
the second one doesn't apply much here either. the "bug" that semako mentioned about an illusion mon disguising as multiple different mons during a game isn't a bug at all; if you switch from your active mon to the last mon in your party, your active mon becomes the new last mon (and so the illusion disguise changes, but not at random). keeping track of say illusion full hp ray vs 88% gengar with sr up can be annoying, but this is the fault of ps for not showing rock damage outside of animations, not illusion.
the third one is where we hit the gray area. the weird thing about illusion here compared to the examples given is that that ohko moves, evasion, and moody were all blatantly broken in addition to being uncompetitive, while i have just argued that illusion is not. in fact, i'd argue that this is the first potentially uncompetitive thing bh has suspected that isn't also broken. but of all the criteria, this is the one to go for.
there's definitely an argument to be made that illusion can be legitimately predicted around, because ultimately it isn't a "true 50/50" seeing as the illusion user is usually pressured to make hard reads in the early stages of the game to eliminate key pokemon before illusion stops putting in work. but honestly, i think that the other side is more credible here.
something kinda dumb is that facing illusion isn't a matter of reading the game, it's a matter of reading the player. what i mean by this is that if your opponent brings in their illusion mon and non illusion mon completely at random, you really have no better option than to risk the coinflip. and honestly, i think that's just a pretty lame thing to have in the meta.
thanks for reading, as always. disagreement is appreciated.