Alas it's too bad the article makes a lot of assertions and assumptions about what iMessage "should" do and be. I agree with a lot of the suggestions but there are also practical concerns to consider when designing a messaging system. iMessage is criticized for allowing decryption of old messages and iCloud backups to share history among devices. But presumably that's a feature that Apple believes its users desire. Every security protocol makes tradeoffs. Merely allowing real-time arbitrary-length communication leaks a lot of metadata about the communicating parties. Yet Signal allows me to send messages of different lengths whenever I please. Presumably that's a feature Signal users desire.