I'm not sure about calling it a new world of open extensions, seeing as Firefox used to support running any extension you wanted and then Mozilla artificially removed that and are now patting themselves on the back for... re-enabling it? Possibly with some extra APIs to make the experience nicer? (Which in fairness is worth something; desktop extensions were wonky on mobile)
They provided tools to make the extensions compatible specifically with the android version.
Before they were curating what extensions worked fine in Android and only enabled those, now the developers can take care of that and mark the extension as compatible.
Wow, I hadn't realized that Firefox for Android didn't have SponsorBlock until now! I'm using Firefox on the PinePhone, it's quirky as fuck but has always had SponsorBlock. I use it with Invidious.
Now, may I suggest NewPipe if you use Android? I've heard the official version refuses to implement SponsorBlock but I see there are forks with it.
What was the reason Firefox for Android did not have a large repertoire of extensions from the start? Was it because of different multiprocess support?
Meh, too little too late. I've already moved on to a Firefox fork that doesn't limit my extensions like this. It's not new to me, I've been living like this for years.
