I have found it incredibly hard to override dark styling, at most you're modifying/merging styles. Dark reader extensions don't work well turning a dark site light, and I've had limited success injecting styles with tampermonkey/stylus. Of course it can be done, just override every style set by the site. But this involves setting a lot of styles and must be done case-by-case rather than using an auto styler. The only thing that works reliably in an automated way is starting with a light style and then modifying it to dark styling.

I also detest the conflation of OS dark preference, browser chrome theme preference, and website rendering preference. It should be obvious to anyone that these are three different concepts where people can have different preferences for each. The cargo-culting in silicon valley drives me nuts.