The only roadblock I’ve found has been the webserial API, which enables users to flash ESP32/8266 or other devices from webpages. It’s super handy for flashing WLED or ESPHome to devices because you don’t have to install any extra software. As far as I know, it has been marked as a “wontfix” in the Firefox bugtracker as they consider it a harmful feature [0]
I mean, I understand the attractiveness, but it's a super-niche feature that wouldn't really move the needle.
The real problem, imho, is the constant glitching on Google properties like Gmail and YouTube. Even if they were really "accidental" (big if), they impact massive amounts of users in their everyday lives, and it takes very little to lose a user forever.
Maybe FF should launch a GMail competitor, and/or promote alternatives to any Google property.
[0]: https://github.com/mozilla/standards-positions/issues/336