Opera 12 can do all that. I'm sad that you ever only experienced shitty browsers which take away this sort of control from the user.
However, in my experience, the DOM for some sites is such a mess that trying to apply user preferences is a hack. I.E. reader view accidentally loses text. Does the implementation Opera has always work? That would be cool, although I'd still avoid Opera for privacy reasons.
Gemini seems to be to throw away all that complexity, which makes user customization easier. I.E. the problem is HTML/JS/DOM complexity, not a browser or its extensions.
1. https://www.ilovefreesoftware.com/29/featured/free-website-f...