iMessage is overall a lot more complicated and integrated than I like it to be. Want to switch accounts, you gotta log your entire user or device out of iCloud. Logging back in will often create issues. Using old Mac/iPhone OS versions creates issues. Messages and attachments are received separately by different devices, and weird things happen when one device is out of space. Deleting messages or blocking senders is per-device. Different devices might miss some messages or even get them out of order. A device waking from sleep often gets messages delayed by minutes (like email), and you're notified a second time for them. And lastly, the "effective. Power لُلُصّبُلُلصّبُررً ॣ ॣh ॣ ॣ 冗" vulnerabilities.
Compared to Facebook Messenger where there's one consistent state in the master server and neatly sandboxed web or iPhone app calling it. And yeah, I know these are partially by-products of e2ee vs traditional, and nobody else has really done e2ee messaging with multiple devices.
The other problem with logging out and back in is that it resets to all iClouds insane defaults that you have to manualky comb over to fix. Its 1000% dark pattern and default nonsense.
Compared to Facebook Messenger where there's one consistent state in the master server and neatly sandboxed web or iPhone app calling it. And yeah, I know these are partially by-products of e2ee vs traditional, and nobody else has really done e2ee messaging with multiple devices.