I don't know about the worst, but it's up there.

And it's not as if this question hadn't been definitively settled by human-factors researchers in the last century. Light text on a dark background is harder to read on a screen. No room for debate, the studies have been done and replicated. There's a reason why computing left "dark mode" in a junk heap full of green- and amber-phosphor CRT monitors.

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...