All of this suffers from the tragedy of open source commons. Public messages (notes) on Nostr are okay at this point, but there are several different protocols for DMs. Imagine being told you aren’t getting your friend’s DMs because their client only supports NIP-04 direct messages, and yours uses NIP-17. Also if you google “Nostr client” the first links will suggest to you as a Mac desktop user a client that crashes with a strange error with no clear guidance how to fix it. Only by reading the Mac specific readme on Github will you be able to open a terminal and paste the correct command that will allow the program to run.
There’s tons of things like this. And Nostr is the best option there is so far. And it’s still this bad.