Yep. Their docs inspire little hope that the protocol will be little more than niche. How to build on top of this protocol without requiring someone with domain specific knowledge is beyond what's offered. Cue XKCD protocols comic.
Given that matrix describes itself as an open standard, neither of those aspects says much about the project other that there's either some goodwill or a PR department.
All of the Matrix/Riot users I know use private, non-federated home servers, but still rely on the project's Sygnal server(s) for push notifications.