This is in my opinion the biggest issue holding Firefox back in the mobile market. I would be perfectly fine with no more feature updates whatsoever as long as all addons worked.
I'm guessing way less than 1% of people would use mobile extensions. I personally do but I don't think most people use chrome on mobile because of the lack of full extension support on mobile Firefox (which btw is coming). I think people use chrome because "everyone else does".
I think you're underestimating how valuable tab groups are to people. I would make a full switch if Firefox could offer that feature on mobile in any reasonable way. Since it's already a desktop extension, I'm just waiting for them to be made available on Android
Sure, but not even close to all. It's been literal years since the change. I was understanding at first, but now it's just becoming frustrating. Things that are very easy in desktop Firefox just isn't possible on mobile Firefox. And yes, I am running Firefox nightly and custom collections for my extensions on mobile.