About compatibility, there are some odd sites that use a Chrome only API or something that FF didn't implement. They are really rare but people that must use one of them to do their job don't have a choice.
Then I intentionally break every single site by using privacy add-ons like uBO, uMatrix, PrivacyBadger etc so sometimes I have to play with them and find a configuration that lets me use a site. In the case of uMatrix it usually means finding the minimum set of scripts that enables enough functionality leaving out all the 3rd party tracking and then saving it. When it's too complicated and I will not use that site again but I must use it, I either disable every add-on on that site or I run Chrome.
Finally, I run integration tests with a headless Chrome, but I develop with FF. If it works with FF it works with Chrome and Safari too.
BTW, I use FF on Android as my primary browser too.
I only have an issue because I set a big disk cache (because data cap). 8gb is fine IIRC, but 24gb causes slowdowns on startups and new tabs. (Also much more of an issue on my older laptop than my newer desktop.)
Doesn't outweigh anything tho.
Everyone has their own ethical standards around this but I think Firefox is clearly seen as the browser to use if you care about the open web. A lot of people therefore feel the need to defend their preference for a Chromium-based browser.
IMO that obfuscates the fact that even non-Chrome Chromium based browsers still affords Google massive influence over the future of the web.
Reality is that non-tech people to know what surfing the web is like with Ad-Block vs non-Ad-Block browsing. Once you teach some one it becomes night and day.
Without teaching someone very few people will step out of their comfort-zone to self educate.
Is letting Firefox slip into irrelevance (by not using it) in the interest of the users, writ large? What developments should we expect if this happens? This is the ethical side of the user.