How odd, my experience is completely different.
I browse all the time in Firefox and Chrome with uBlock Origin and Pi-Hole. Not much is broken. In the rare case something is broken I flip DNSCrypt on and use Safari/Edge which don't have uBlock Origin installed. That happens like, what, once a year?
It would be nice if Firefox had a page that listed every setting that is changed from a default value in one place. You'd still have to investigate extensions separately, but at least all those obscure hidden settings you've changed accessible and visible in one place.
On about:config, sort after the "Status" column. That'll give you a list of all modified values.
And more importantly, when I need to bypass these safeties by using another browser, I'm doing so intentionally: I know this site is trying to move outside my security comforts, and can address it accordingly, rather than any given website abusing my privacy.
And of course, if I switch browsers just for sites that don't work in my Firefox setup, they're loading in a browser I use for little else... so they don't find much anyways.
In theory i'd rather use Firefox over Safari. However in practise, a lot of stuff doesn't work properly in Firefox - because of some extension or some about:config setting i set after reading posts like this.
When that happens, i always revert to the trustworthy Safari which just always works (...and has proper pinch-to-zoom, which in my opinion is a very basic feature Firefox is lacking.)