Extensions are one thing. Even if a distro comes with some Gnome extensions, you can just disable them. Ubuntu puts custom patches on the Gnome packages they ship. Those can’t be disabled, and they could potentially interfere with extensions that don’t expect them to be there. That’s my problem with Ubuntu’s approach to Gnome.
I understand that you don’t like vanilla Gnome, but I still wouldn’t recommend Ubuntu to anyone, especially noobs, as a desktop OS, because of the myriad issues with Canonical’s approach to modifying the source of the packages they ship.
It’s the same reason if anyone reports a bug to any of my software, and they say it happens on Ubuntu, I’ll disregard it unless they can replicate it on an OS that doesn’t patch their packages that way. Canonical is responsible for fixing the bugs their patches cause, and they’ve added tons of extra triage work to devs who have to determine whether Canonical fucked something up or there’s actually an issue with their code.
I get not liking a game about SA and incest, but how about just not play that game?