I'm gonna go on a limb here and say it's probably some fuckery Denuvo's causing. Whenever it's removed from a game, the performance actually improves. Last year it was haphazardly added to Doom Eternal and the performance became noticeably worse. Doom Eternal was one of the most beautifully optimized games for PC prior to Denuvo being added, so people actually had a frame of reference for how the game is supposed to perform. Then Denuvo was removed and it went right back to playing smoothly.
This is why I'm gonna wait it out a bit before getting it. Only other option is to get it for my base PS4, which, at a cursory look, isn't ideal (it apparently run at 45 fps).