Wondering if this is about Darkvector (normal name, @Arcane21)? DarkVector (CamelCaseName, @Malvineous)? Vector-DarkCSS (@Malvineous too)? Or others/all 3 skins?

This isn't just vector - it applies to any dark skin, where mw core styles assume a white or white background and thus components are styled with white backgrounds to match this expectation.

It's not really a valid expectation, but nor is there really a good way to address this directly without some overhaul of how core and skin styles interact in the first place, at least that I can think of.

Also applies to things added by extensions, and frameworks such as oo-js.

if the Theme extension ever gets merged into core (T122924), this ticket would be easier to tackle. :)

In T66731#2932966, @SamanthaNguyen wrote:

if the Theme extension ever gets merged into core (T122924), this ticket would be easier to tackle. :)

How so? The problem here is the explicit styling on various UI blocks, and skins having to then explicitly override all of them (which tends to be particularly bad for stuff added by extensions, js elements, and anything non-static). At a minimum, we need better generic styles applied to the blocks, but ideally I'd say what we want is probably some sort of framework to specify generic styles within the skin that then get applied to all of these (like ooui themes, but done in a way that's actually feasible for the skin itself to implement) - basically, reverse the process.

Theme seems like it's just affected by this bug same as the skins themselves.