I’ll only answer the first one.

Achievement systems full stop. People who value completion through achievement systems are fucking uncreative persons who need to find a different hobby or reconsider why they enjoy theirs. From a dev standpoint it’s just a way of lazily padding a game.

I’m not talking about completionists of actual game content like collecting all the stars in a Mario game, or catching the 151 pokemon, but moreso the “silver trophy” for killing 2000 grunts or whatever bs achievement ideas they decided to arbitrarily create. You’re diluting the art form.