The problem is that as much as I want Firefox to be a better browser than chrome - Blink is still a far better rendering engine than anything else. Every other browser either has inferior performance (including Firefox) or is just a fork of chrome.
I spent a year trying to use Firefox after being a chrome user for well over a decade - I eventually switched back when Mozilla started adding the same tracking features that chrome started out with years ago. Mozilla seems to be going down the same path, albeit several years behind and slowly. After that I just didn’t see a reason to not just use chrome if I’m going to have to neuter tracking bullshit anyway since it’s still much more performant than Firefox.
V3 complaint UB exists (UBo Lite) and works plenty fine save for what even I (as a power user) would call power user features. It’s very annoying that Google is going down this route, and I really want Firefox to be the better browser, but I just don’t think it is yet. During my year of usage you definitely can notice the performance difference and the inconsistency in certain webpages.