Seems to be an organizational thing, at least some who try to work with- or are part of the Gnome Foundation mentioned this. Apparently KDE e.V. got a way more flexible structure with work groups, easier ways to propose changes etc. while Gnome gets awfully stuck with their panel/council structure (not sure which one is the right word in english).

When mentioning the problems with extensions (rather furiously since I just lost some work again and installed KDE) I was told both: Go on an create a PR, but also that “this was discussed and a panel decided against changing anything”. Obviously no one will waste dozens, if not hundreds of hours of their time even just creating a Proof-of-Concept for sth. like an extension API if some authority already decided that nothing is supposed to be done about it.

As long as your Gnome environment can’t gracefully crash without taking absolutely everything with it (like with KDE or other DEs) there’s no way in hell anyone should use Gnome on computers where actual work is being done, let alone something critical.