What extensions are you using? I (anecdotally) never have any of the issues you describe. And I'm on my computer 12+ hours per day, most of which is spent galivanting across the web in Firefox. Are you using a forked version of Firefox?
To me FF is just as fast in general browsing than anything else. I routinely try other browsers and I just feel "wrong" using any of the Chromium based others of Edge/Brave/Vivaldi when FF needs us right now. It needs the us to stand against non-open source web browsers and as an alternative engine to the web. I really like Vivaldi and would be my 2nd choice (then Edge then Brave, refuse to use Chrome) but it isn't open-source nor does it do anything to protect privacy.
If FF is giving crashes, issues at sites etc please try at least refreshing your install in the options and don't install so many extensions. Even better backup your bookmarks and uninstall it while making sure to also delete all users\$username\Appdata folders as well then reinstall.
I fall back to edge if I have an issue but it's not common.