I think that the concern is whether a number of websites might stop working with Firefox if Chrome users consistently represent ad revenue and Firefox users generally don't.
I use Firefox, but it has relatively-limited marketshare in 2026. A lot of people just browse on mobile devices and on Android devices, and there Chrome's probably the default browser.
https://gs.statcounter.com/browser-market-share/
Chrome at 70.25%.
Safari at 15.72%.
Edge at 5.14%.
Firefox at 2.19%.