I guess it would be boring or predictable to have the antagonist never reveal a true motive. But maybe writers could learn from Glass Onion, which kind of does this in reverse: the villain SEEMS like a canny mastermind, but actually he's just an idiot who got lucky.
I'd love a villain who's in charge of the Klan and everyone's like "What's his secret goal? What's he plotting?" and then at then end they're like "Oh...he's just a bigot." That seems much truer to real life to me.
The Peacemaker show actually did a pretty good job with this, although I guess the clan-allegory villain wasn't the main bad guy. My memory is hazy.