Ive been wary if firefox since wheneved it was they decided it was okay to shove "pocket" into the browser. These days i dont see mozilla as anything other than anti monopoly insurance for google, which they obviously dont need anymore.
Mozilla as a company has just been a decade of one poor decision after another adding more bloat and doing nothing meaningful to counter chromes near monopoly.
Vivaldi isnt perfect and brave has its baggage, but at least they actually include adblocking out of the box, a feature that just about everyone wants. Sure its easy enough to install an addon to firefox for it but the fact that you even have to do that should tell you everything you need to know about who mozilla is actually working for.