The main reason for mobile being underprioritised is that many of the mobile devs (who are based in Rennes in France) are doubletiming with helping the French government project and so are quite stretched for time.
Also, for better or worse, we have entirely separate codebases currently on Web, iOS and Android. The reason we do this is to ensure that other app developers can use the same proper native matrix SDK in their apps rather than be forced to use a device abstraction approach like React Native. However, it means that typically the web SDK leads the way (as it’s the easiest test bed for new features, and several of the core spec team work on Riot/Web, so new stuff happens there). However, we’re starting to see the balance shift: the new Android SDK and app is more advanced than the JS SDK, and we might even experiment with using Kotlin Native as a way to share that code to other platforms.
Eitherway: we’re aware that mobile needs more love and investment and we’re trying to fix it :)