Gave up on FF a month ago because it was just too damn slow, but I didn't want to go back to use Chrome because I don't want to have to install a ton of addons just to have features that should be baked in the browser by now.
I found Vivaldi and besides really minor things that I'd like to have, it looks like the perfect browser. Highly customizable, fast, and with full access to the Chrome addons. Not going back to either of the other two for the time being.
If you're finding Firefox to be noticeably slower than Chrome/Edge, disable extensions until you find which one is slowing it down that much. On a clean install they're very comparable in speed.
So, you are back to Google dictating what you can and cannot have. Lets not pretend that Vivaldi has much influence over that (if any at all). They ship Chromium with trivial/irrelevant tweaks. If that makes you feel good, more power to you.
However, people underestimate the amount of influence Google has in the Chromium ecosystem. At this point it's their way or the highway (i.e. Firefox/Safari). None of the companies shipping Chromium based browser have either the competence, willingness, or team to ship a functional browser that is meaningfully different. It's just lipstick on a pig and magical thinking when it comes to privacy.
Firefox works well enough for me. If there are websites that work less well in it, I've long stopped caring about those. All the essentials that try to sell me stuff work just fine. Financial dependence does that. People put in an effort to make shit works when money is on the line.
The less addons I need, the better. As long as I can block ads with uBlock Origin and handle a few other small things, I'm good.
I gave up on my freedom a long time ago since I use gmail and outlook for everything. I leave those things to people more enlightened than me, I just want things to work.
I found Vivaldi and besides really minor things that I'd like to have, it looks like the perfect browser. Highly customizable, fast, and with full access to the Chrome addons. Not going back to either of the other two for the time being.