This is really not accurate. Matrix is not designed to be a super privacy first protocol. It's like Lemmy in the it's designed to solve a problem and be a useful federated collaboration tool. It borrows features from a number of popular messaging platforms. Message history is stored on the server but encrypted client side so privacy is preserved. It supports group chat rooms. It supports voice and video. And most importantly, it supports bridges- you can connect your matrix to other services that are completely incompatible with matrix using a bridge. Perhaps the best example of this is Beeper, which is built on matrix. They are trying to replicate the user experience of the old app Trillian- beeper can link with a number of chat services including Google messages, slack, WhatsApp, telegram, signal, etc. Thus you get all your chats in one place.