iMessage is so riddled with problems from using weak RSA key sizes (1280 bits), to using RSA in the first place (thus no forward secrecy), to apple essentially managing the public keys for the user (which allows transparent MITM due to lack of public key fingerprints).

Also, both iMessage and WhatsApp are proprietary, thus it's almost impossible to verify the code you're running is safe. You're right in that E2EE has become more common, but seeing how the intelligence agencies have targeted major vendors like Crypto AG and RSA, we should be extra careful with popular, proprietary systems.