The difference between the Fediverse and a closed system like reddit is that it’s open and we’re privy to haphazardly implemented functionality and bad API documentation.
I work on big closed source web apps for a living; they’re just as haphazard and badly documented, it’s just all closed.
I used to be really into theming. But now, the default Breeze and Adwaita look good enough that I haven’t bothered wanting to change them in a couple years.
That and thmes always appeared to be some degree of “broken” that I just don’t bother anymore.
I do always change the cursor to the black Adwaita one, even on KDE. It just feels right to me.
When I did still use themes, Numix, Arc Dark, and whatever “flat” themes that I could find were my favorites.