I apply scrutiny in the form of very carefully vetting the author's identity and reputation. At the end of the day that seems to be a fairly common and reasonably effective approach.
> XUL-era extensions had vastly more power than WebExtensions. They were equivalent in power to native executables
That was an important feature, not a bug (IMO). Sure WebExtensions are nicely sandboxed away from the OS, but the threat posed by a malicious version of uMatrix or Dark Reader is nonetheless difficult to understate.
Certainly many users made poor decisions. Certainly there were valid technical issues at play. But let's not pretend that all users are irresponsible or that there weren't serious drawbacks to what was done in terms of lost functionality. Some of the modifications I made use of still haven't been replicated in WebExtensions due to lack of ability (AFAIK). The only solution I'm aware of would be to patch the browser myself and recompile it, which is an _incredibly_ high barrier to entry (and that's before the ongoing maintenance burden).