Mozilla: what? acquire a bookmarking service?
Angry crowd: no! develop your browser!
Mozilla: ok, got it! I'll make a VPN service!
Angry crowd: WORK ON YOUR FUCKING BROWSER
Mozilla: AI? Did I hear AI from someone over there?
E.g. VPN, search, bookmarking service - great. Charge for them, have the money go into browser dev, focus on privacy and be done with it.
I feel like once you state these questions out loud it becomes clear that none of this cause and effect necessary to make the argument work is being critically thought through at all.
There was a time when this complaint about core browser experience had some legitimacy and that was in the 2010s up through 2016. They rebuilt their whole engine into Quantum in 2017, which was a major leap forward. And ever since then the differences have been real, but subtle. Meanwhile Google has leveraged its dominant position in search, and it's major investments into Android and Chromebooks to push people to its browser. They've also used their revenue to invest in an embrace extend extinguish strategy in the browser space.
The vast majority of the vibes about Mozilla transgressions are more like a self-perpetuating oral tradition than a thoughtful narrative grounded in causality.