Whereas on my i5 thinkpad ('14 t430) I had to switch to chrome as my browser, which was annoying, but even on a clean win10 insstall w/ only FF installed, it would peg the cpu hard. Don't know why, as I still use it as my primary browser for my desktop as well as android phone, but ever since Quantum there just seems to be a significant number of systems that are incompatible with firefox.
Oh, and before anyone asks, on the thinkpad the performance issue was still present on a debian stretch install as well.
Just because it works on your system doesn't mean this isn't a bug they need to fix.
It is a showstopper. I don't care about new features if it can't handle basic stability.