You have to jump through a bunch of hoops to use them, to the point that only a handful of people do it, which decreases the motivation for anyone to put effort into supporting Firefox for Android in their extensions.
It really seems to me like Firefox wanted to prevent a healthy extension ecosystem on Android, but they have not been transparent about their reasoning.
Whataboutism isn't a particularly useful response. Firefox used to have thousands of supported extensions and allow users to install unsupported extensions. Now it doesn't, deliberately, and I would like them to reverse that decision. The fact that a more popular browser has a worse situation is irrelevant.
You can run a fork of Chromium that supports most desktop Chrome extensions: Kiwi Browser. That's not so different from having to run an unstable build (nightly) or fork (Iceraven) of Firefox.
