Used to run chrome for it too. Never understood why it should impact which browser you use for everything else ...

Better how?

This isnt really true anymore. Firefox has caught up in devtools, and has superior tools when it comes to animation debugging. Performance also isn't worse than chrome, in fact I've found that FF uses a lot less memory than chrome does.

The only time I open chrome is to use an occasional WebApp that needs the Bluetooth API or something like that.

voluntary subjugation

I don't think that is true today. At first Firefox had better tools but developers didn't do the smart thing and developed for Chrome.

At the time it was indeed faster, not really an issue today either. Also the writing was on the wall for quite some time.

On my 2017 Ultrabook with only 4gb of ram, Firefox stalls repeatedly & has long stretches of being entirely unresponsive after half a dozen tabs, and gets worse from there.

I have some delay where a navigation might be delayed some, but Chrome doesn't ever lose input and generally manages to keep going.

Even on a desktop with 64GB ram, Firefox gets slow over time & needs to be restarted when I have a significant number of tabs open. Tab auto-suspend extensions generally "fix" the problem, but it's been frustrating that whatever the on-page performance is in Firefox, the app itself feels so prone to bouts of unresponsiveness.

Please be more precise about what you mean by "significant number of tabs", is it 50, 200, 500, more ? Because on a 16 Gb laptop, I don't have any problem with 50 tabs open with Firefox.