Worst in the context of ergonomy as it is dictated by the websites/mobile applications and not the user, like the choice of computer screen hardware and settings or choice of chair, desk, mouse...

Exactly. There's no reason why an individual user shouldn't prefer dark mode, and there's no reason why a site shouldn't offer it. But if you run a popular site, it's an asshole move to force it on your users, as so many sites are doing these days.