It isn't a matter of "failing to observe": without the necessary API, extensions cannot be ported. I personally looked into rewriting the extensions I needed a couple of years ago, I figured out it was impossible and I gave up.
Some very important extensions have fortunately been able to pressure Firefox into supporting them, but the typical Firefox user who depends on some niche extensions has no clout.
Such is life. I'd rather have Firefox survive and continue to compete effectively than go chasing after perfect compatibility with those extensions I've also temporarily lost the ability to use until the necessary APIs land.
If Mozilla could have done both, Mozilla would have done both. They could not. I get that that's super frustrating. I'm not happy about it myself, because the change broke my workflow a little as well - until I engineered my way past that, because I'm a grown-ass adult and I solve my problems, or learn to cope, instead of whining about them - and also because I put myself on the hook for a Firemacs reimplementation that can't land for probably another year at best. That's annoying. I get it.
But slinging vitriol on the subject obtains nothing and aids nobody. It makes the people who do it look like jackasses, it makes the people who do the actual work feel like they can't win and may as well not try, and it makes everyone else embarrassed both on the behalf of the whiners and for their own sake in being associated, however loosely, with a community so full of Tumblr-grade drama. It's embarrassing and stupid and pointless and counterproductive and I wish people would stop. There are better ways to spend the same effort - like, for example, contributing patches to the webex implementation. Hard work, I know, and whining is easy. But that doesn't really play in favor of the whining, either.
(Yeah, I get that you're not really a major example of what I'm complaining about. You just happened to be right here when I lost my patience. All the same, though.)
Some very important extensions have fortunately been able to pressure Firefox into supporting them, but the typical Firefox user who depends on some niche extensions has no clout.