There is only three hard parts of e2ee. 1. Making it actually secure. 2. How does a user logging in to multiple locations share the key. 3. Full text search.

There is only three hard parts of e2ee. 1. Making it actually secure. 2. How does a user logging in to multiple locations share the key. 3. Full text search. It would be hard for discord to do 1 and make everything e2ee. But the casual nature of discord users makes 2 and 3 a deal breaker.