What about ignoring that 0.1% of the websites that are so badly made they don't work on firefox? Do they really deserve your attention?

Or keep Chrome (or Chromium or even Edge if you have it installed anyway) for the rare use case when Firefox won't work?

Sometimes yes. That 0.1% of sites could be me trying to buy a movie ticket or something. I'm not gonna cancel plans with a friend to see a movie because I need to protest Google that badly.

Did that really happen or is that theorical? I've never been unable to buy a ticket on firefox.