But that's cyclic reasoning. Nothing that you need/want will be on matrix if you (and everyone else) does not think it's worth to make what you need/want be in matrix..
I don't need EVERYTHING to be in Matrix, just the things I'm interested in. So I'm happy when I see a push to have those specific things there. This is the same argument as to why I don't use Reddit anymore, despite Lemmy/Kbin having only a fraction of the content.
It also helps the fact that Matrix is very flexible when it comes to mirroring/proxying other protocols. I can easily access IRC communities from Matrix, for example. The integration in that direction is nicer than requiring discord channels to add bots that parrot an IRC chat.
Note that "secrecy" and "privacy" are often understood in Security lingo as different things. One protects confidentiality, the other one protects anonymity.
It's possible to have one and not the other...
You can have a very private system through onion routing but have the contents of the messages exchanged be in plaintext, open to the public. Nobody will be able to know the one who wrote the message was you. But they can see the message. (then there is privacy, but not secrecy).
Or you can have very strongly encrypted communications (say HTTPS) but have the DNS exchanges (or the TLS handshake, or the IP addresses) be in the clear, so people in the middle (eg. your ISP.. or your workplace tech guys) can know exactly that the packages are sent by you and where you sent them, even if their content is encrypted. They can know which service you tried to access to, for how long and how many times (so you have secrecy, but not privacy).