DM - "Psyche! No, that particular two-armed bipedal creature over there is actually an aberration. Your turn is wasted, you should have chosen differently."
PLAYER - "But...the spell worked just fine previously on these things! And you described this one as pretty much exactly the same as all the others. How am I supposed to tell the difference?"
DM - "Trial and error".
PLAYER - "You mean wasted turns.'
DM - "Not my problem. Them's the rules."
Okay.
What happens if...y'know, you have DMs that
aren't jerks, but who expect the rules to be followed unless they're obviously
broken, rather than just kinda dumb?
Because it isn't just jerk DMs who would do this. The spell
explicitly says that it fails against nonhumanoids (rather, that non-humanoid targets automatically succeed on their saving throw, which terminates the spell.) You are assuming that
absolutely all good DMs would read that and think, "Hell no, that's awful." This is not true. Plenty might think, "Huh, that's kind of a bad spell. Hope my players are ready for that!"
Perhaps they want to de-emphasize poison use. Not very "heroic" for a good guys game, I guess?
Wouldn't that be exactly the sort of thumb-on-the-scale behavior that 5e fans (claim to) hate, though?
Although, if it did require you to target a humanoid, it would functionally act as a counter-intuitive, off-label humanoid detector...
Presumably only against people you dislike, since it's quite clearly a mental assault.
I'm sure the 2024 rules will work fine as written. As long as you don't try to use previous rules to judge the 2024 rules by.
Besides, the 2024 rules aren't even fully published yet. Until the PHB, MM, and DMG are ALL published, the rules are not yet published and are incomplete. Arguing about them is, well, its the internet. So go to it!
As Micah said in reply to this: We already have the PHB, which contains the spells. So we already know that. We already have the DMG, so we know what's in that too.
People are complaining because we have been given "previews" of the MM, including explicit indications about such things as "many but not all goblins are now fey" and "gith are now aberrations" etc.
The only possible alternative to "this is what the 5.5e MM will actually look like" is that WotC is, for some ungodful reason,
lying to their own customers about what the books will contain, and actively putting up unrepresentative, out-of-date monster blocks. Despite the goal of their efforts being to show off what the 5.5e MM will contain, they would have to be actively
falsifying that, in a way that makes it look significantly worse than the actual thing.
I don't really think either end of this dilemma turns out well for your position here. Either you're just choosing to ignore the previews, pretending we live in perfect ignorance until the book is actually available to be picked up, or you're asserting that this whole preview campaign is a massive
falsehood perpetrated by WotC for no discernible reason for which the only possible "good" effect could be people buying it and then exclaiming, "Oh, thank God they didn't do the stupid things I was worried about."
I'm not really sure either of those are what you want out of this situation.