@isotopp I'm not actually against your conclusion, it's not user-friendly and not in any way a serious alternative to other chat clients or networks, but to at least to offer some explanation:
matrix.org is, much like mastodon, the name and website of the protocol and seems to not being aimed at 'users' much. The default portal of the element client (the web-app, not the ios/android app) looks much more like you would expect. (e.g. https://element.cccgoe.de/)
@isotopp
So it relies on you already knowing which instance to join (e.g. your local hackspace) and does little to advertise which one to choose or what's their TOS/CoC/Privacy Policy. It's modeled much more after IRC than modern social media.