I work at MS, tried to use Firefox but couldn't because FF doesn't integrate with the Windows cert store. Crucially, this keeps Windows Hello (TPM auth) from working, which makes it useless for any internal websites. For a while I used a hand-compiled PKCS#12 plugin that bridged to the cert store, but that was extremely fragile and eventually I gave up.
I think this is probably a major blocker for many enterprise users, and wish Mozilla would have fixed it.
edit: it looks like they may have fixed this in the past couple years, though you might have to go poking around in about:config.
Current MS employee here. For a time this was true, but FF recently added this integration. No about:config needed, there’s simply a checkbox under the FF security settings. Since this was added, I have gone back to using FF as my daily driver, and I haven’t really encountered any other friction.
Firefox not integrating with the Windows cert store is actually a good thing in many use cases. The ability to have an alternate browser that's not integrated has saved my butt more than once.
