If we can solve an issue on a specific layer, such as the metadata privacy of recipients and senders at the application layer, that is definitely progress. 

IP issue is a network layer issue and needs to be resolved at the network layer. 

Moreover, the solution to the recipient's metadata privacy issue is the same as the solution for the sender's metadata privacy issue: both are addressed by continuously updating addresses. 

 Sure, it's progress. But if you have progress in one, but doesn't solve the other layer, you can't claim being better. Sorry. I have seen too much of these BS with "private" comms in the last 20 years. people love to fool users into more complicated stacks and then leaving IP all there to be fully traced by servers.