Sure but I only use Firefox (no other browser installed (except Edge on Windows)) and I don’t have any issues; so some none-trivial portion of the web doesn’t require Chrom(ium) specific behaviour.
The only websites I seem to have issues with are usually trash sites anyway. All my regular sites like banking, Google Docs, Office 365, finance, etc. work just fine in Firefox. I do find its performance not up to par with most sites that might have a very JavaScript heavy app for gaming and such.
Google websites intentionally degrade performance if you browse from Firefox. Facebook Messenger's E2E only works on chromium browsers. There are many websites that show popups to use chromium for the best experience. I do get it, these aren't privacy-friendly websites, but for professional purposes, lot of people are forced to use chromium browsers or user-agent strings.
