If you were on the web in the 00s, you remember web sites saying things like "This site works best with Internet Explorer" or, even worse, using technology like ActiveX which meant "this site ONLY works with Internet Explorer on Windows, the rest of you can get stuffed." (There was an Internet Explorer for Mac at that time, but it was garbage and couldn't run ActiveX content).
Today, that's Chrome. But this time it's different. It's not driven by web sites who explicitly make a tech choice to only support a single browser. What's happened is that all the developers, testers, and frankly the end users have all just decided they'll only use Chrome. They only test web sites on Chrome and all their users who report problems are reporting them on Chrome.
At work I am increasingly using enterprise software that throws errors if I use Firefox, but magically just works if I use Chrome. It's different this time because the developers don't seem to care (the web site/software doesn't include non-Chrome accommodations the way web sites used to include "if IE6 do X" code) and the business isn't even advertising "this only works if you use Chrome." I don't find this in FAQs like "Q: X doesn't work, A: Try using Chrome." It's just that a lot of stuff breaks in weird ways if I use Firefox, and doesn't break at all if I use Chrome.
Monopolies are bad for the end user/customer. Diversity forces innovation. We need significant numbers of people using something other than the same thing most people use.
That's one of the problems with Firefox adoption at the moment. No normie will use a browser that might not work on a given site, but no developer will test for the 1% of users
I don't know how many normal sites even have a problem with Firefox. I guess only some small, niche web apps, but otherwise most people would see no difference. Even if developers don't explicitly test on Firefox, almost all features will still just work (at least for normie usage). Power users might encounter some challenges, as the post describes.
nameisp.com, snapchat.com, and teams.microsoft.com are the ones I can think of off the top of my head. nameisp.com is especially frustrating, because it doesn't have a "doesn't work with Firefox" banner, it just inexplicably breaks on Firefox.
Also, Firefox and Chrome handle broken XML differently, which has broken a number of internal websites for me.