I just want something where I can import stuff (most importantly web pages, pdfs, epubs), read (on my e-reader), mark things/take notes, search and turn highlights into citations.

The desktop version of Citavi and Zotero seem extremely overloaded. The web version of Citavi is the closest to this I've seen (it has a mode for highlighting), but it still absolutely sucks.

Maybe I don't get the hang of how real researchers or scientists do things, but so far what I mention above is the core of what I really need (mainly for personal research, but also the limited amount of scientific writing I've done).

I read about Zotero theoretically supporting these features, but when I last checked it out (about half a year ago) it looked antiquated, seemed to do a lot of things I don't care about and made the things I want to do so hard I was immediately disappointed and stopped bothering.

Are there any products (preferably FOSS, of course) that cover my use case? Is it possible with Zotero after all? I have tried Worldbrain Memex, but it also has such cumbersome UX it's not worth using.