Meaningless? I value private communication with my friends and family. I don't exactly need anonymity there. In fact I want the opposite. In the absence of phone numbers I would be adding very explicit metadata on my device to distinguish between my friends.

Signal has taken measures to limit its ability to know who I'm sending and receiving messages from. Though it's still possible by mapping my IP address to me. So yes there is still a centralized metadata problem, but I'm not letting perfect stand in the way of better.