Oh no. Firefox extensions? FF's treatment of its extensions would be the reason I stopped using Firefox after nearly a decade of using nothing else: the extensions became useless because FF repeatedly broke all its extensions every few weeks, nobody could keep up, and eventually all the extensions I relied upon to keep FF usable fell into disrepair (I hear it's better now, but it's too late, I moved away). Chrome, with an actual extension API rather than a big ball of mud, has never broken an extension for me in a year and a half of use with dozens of extensions, despite massive progress in that time.
So if GNOME is modelling its extension API on FF's, it's not a good sign. If it models it on FF's except treats it like an API and doesn't break it at the drop of a hat, that might work better.
(Again, I don't really know how Emacs has avoided implosion despite using the same 'big ball of mud, everything is available' approach as FF extensions do. I suspect it is simply treating its interfaces like a programming language designer would, i.e. extremely conservatively, taking *decades* to deprecate *anything*, so by the time your extension moves from using deprecated interfaces to breaking because they're removed, the app itself is too obsolete for anyone to care about it anymore. It only just broke old-style backquote, for instance, and that started emitting deprecation warnings something like fifteen years ago.
Perhaps if people would consider that they are kicking all their users every time they deprecate a stable interface it might help. I understand that Emacs developers ritually cut off and sacrifice a body part to the cons gods every time they intentionally break anything that external Lisp is relying on :P That attitude might help too, but it seems to be almost unique in the 'just break it dammit' free software community right now.)