The decryption problems I've experienced have a been fixed a while ago. There was a push to fix these last year or the year before that, and at this point I'm pretty sure only some outdated or obscure clients with old encryption liberties still suffer from these problems.
The huge amount of unencrypted metadata is pretty hard to avoid with Matrix, though. It's the inevitable result of stuffing encryption into an unencrypted protocol later, rather than designing the protocol to be encrypted from the start.
I've had similar issues with other protocols too, though. XMPP wouldn't decrypt my messages (because apparently I used the wrong encryption for one of the clients), and Signal got into some funky state where I needed to re-setup and delete all of my old messages before I could use it again. Maintained XMPP clients (both of them) seem to have fixed their encryption support and Signal now has backups so none of these problems should happen again, but this stuff is never easy.
Yes, messaging protocols, especially federated ones, are never easy. I just wish we could have skipped the three or four years when Matrix was basically unusable for the average user because end-to-end encryption was switched on by default. Perhaps a clean redesign would have been better. Now they have to change the wheels on a moving car.
The huge amount of unencrypted metadata is pretty hard to avoid with Matrix, though. It's the inevitable result of stuffing encryption into an unencrypted protocol later, rather than designing the protocol to be encrypted from the start.
I've had similar issues with other protocols too, though. XMPP wouldn't decrypt my messages (because apparently I used the wrong encryption for one of the clients), and Signal got into some funky state where I needed to re-setup and delete all of my old messages before I could use it again. Maintained XMPP clients (both of them) seem to have fixed their encryption support and Signal now has backups so none of these problems should happen again, but this stuff is never easy.