I don't agree that Matrix has excellent clients for all platforms - IMHO, only Riot Web/Desktop is usable, and that only in comparison to other open-source messaging software - it doesn't compete against pretty much anything that people make money off of. Riot iOS and Android both make it nearly impossible to handle a large amount of chatrooms, IME. And nothing else implements even most important features of Matrix.

The developers badly need to invest in a UX engineer, but are currently stuck scrambling for money as their corporate sponsorship ran out.