> Should not have even started the app with on service, non-public messages.

Maybe the service you think they should have built is not the one they wanted to?

It's not a private messaging protocol. It's an ActivityPub implementation, a public-posting protocol.

In fact, DMs in Mastodon are broadcast to anyone mentioned in them; if you @jsled@mstdn.io in a DM to your buddy, talking shit about me, it gets posted to my inbox!

If you want secure private comms, use Signal, use Cwtch, use SSB.