I've been using Firefox as my main browser for a long time and over the past couple of years I noticed an uptick in websites that wouldn't work lest I used Chromium. For instance last week I had to use a crappy HSBC website that wouldn't let me login in Firefox (it would just hang) while it worked in Chromium.

It's still very minor and I can't even come up with a 2nd example off the top of my head but it does definitely happen from time to time.

If anything these few cases only makes me value Firefox even more, I don't want to enable the Chrome monopoly.