That's where you're wrong. Firefox market share is dropping month on month for the last decade with no sign of turning around. Blink is forcing Manifestv3 soon which doesn't support many features uBlock Origin needs to work effectively. Sure, other Chromium forks claim they'll continue to support v2, but we'll see if that lasts after Google removes the code and they have to actually maintain Blink for the first time ever. None of the forks (except maybe Edge) have the engineering staff to keep up with rebasing against Blink.