My only real problem with Sun and Moon, and by extension USUM is that in order to promote their new gimmick, they pissed on the old gimmick, by making it seem as though Mega Evolving a Pokemon was an act of cruelty in some cases.
Like... yeah, Mega Glalie's jaw is functionally broken, but Mega Evolutions are transient forms made exclusively for battle. Trying to make a Mega Pokemon do mundane shit they're physically incapable of doing instead of using them in battle as intended just to prove a farcical point seems way more casually cruel.
If nothing else, it did lowkey reinforce the idea that Alolans are pricks who tend to demonize shit they don't understand that the Sun/Moon chapters of Special picked up on.