Tor lost all credibility for sticking to firefox, not to mention all the other security issues discovered over the past few years
Also Torbrowser uses a security-hardened version of FF LTS, so it's pretty useless to assume FF vulnerabilities all apply to Torbrowser.
Firefox is only now catching up in regard to site isolation.
Yes, but firefox has other benefits. if only that, a cooperative team that's happy to take patches as part of the "tor uplift" project, whereas Chrome wants to fingerprint every single user and makes projects like TBB harder to implement.
Also, i personally think it's a good thing that TBB is a noscript-first browser. Everything involving JS, even with a 10 feet pole, is a glaring security issue. So yes you can enable JS and the site isolation isn't the best, but truth is just use "Safest" mode and you'll be fine.