Honestly, the whole model of "you can customize every detail of your page (and not the user) but you also have to implement basic accessibility and consider screen resolution/orientation, reduced-motion, prefers-color-scheme, etc., etc.), for each and every single webpage, is imho inherently broken.

The sad thing is, they could in most things (except reduced/animations) just not do that and the browser does accessibility & stuff for you and you have a lightweight site. But that's not how businesses (and developer curiosity) work. Also, progressive enhancement instead of graceful degradation most don't do.

Btw, to the Indieweb: you don't have to define a text or background color: browser does that already. And you have to care for prefers-color-scheme now. Please keep CSS to layouting.