Firefox, IMO, is a good browser.

It has laughably low market share.

Browser market share has very little to do with the quality of the browser after a certain point. Safari is a pretty good browser, but it has a decent market share due to Apple's policies. Google Chrome is a pretty good browser, but it has crazy market share because everyone uses Google services for everything and Google pushes Chrome incredibly hard, to the point of intentionally breaking their websites and/or arbitrarily disabling certain features in non-Chrome browsers.

Browsers don't really compete on their merits.

FWIW, I'm also looking forward to having proper Firefox on my phone.