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.
In the case of Brave and Vivaldi, they add their own undesirable parts (Brave adds crypto bullshit and Vivaldi is closed-source, so $DEITY knows what they’re adding).
Librewolf is open and doesn’t contribute to the Chromium monoculture; so it’s the best option