I've had bugs where the site doesn't work in Firefox but works in Chrome, but as far as I can tell, those were always caused by the aggressive privacy settings I use in Firefox (whereas the Chrome profile is mostly default).

I'm not particularly concerned with the article's complaint about onboarding. The problem is that Firefox is simply slightly worse (less polished, often slower) in many, many aspects.

On Desktop, Firefox is quite usable, even if it is a bit less polished than Chrome.

On Mobile, it's another story. The only thing saving it is the fact that Chrome doesn't let you install extensions, so you have the choice between an ad-filled web on a browser that runs well, with the ads slowing you down (with Chrome), and a clean web in a slow browser with an unpolished UX and infuriating bugs that don't get fixed (with Firefox). So far, I'd say the two experiences are comparably annoying.