I think Miser is only clearly good in a game with no draw, no trashing, and no attacks. And well, that's pretty boring.
In the 3-card kingdom "Scrying Pool, Worker's Village, Miser", I'm going to play with multiple Misers.
Edge case.
No, it's a basic counterexample that should illustrate why I think the statement is bonkers.
Draw makes Miser better, not worse; other trashing may or may not want me to go Miser (it really depends on the other trasher and the rest of the board); and I doubt the presence of attacks has on average a big impact on whether I go Miser or not (on most Cultists boards you clearly don't want it, but in general attacks prolong the game, which makes Miser a bit better).