You and the person you are communicating with must both not use iCloud backup. And since apple pushes the backup features pretty heavily, you can be reasonable sure that the person you are communicating is using backups. IE, you cannot use iMessage.
I got off all Apple products when they showed me their privacy stance is little more than marketing during the CSAM fiasco, but IIRC the trouble with iCloud backup is it stores the private key used to encrypt your iMessages backup. Not ideal to be sure, but wouldn't iMessage users be well protected against dragnet surveillance, or do we know that they're decrypting these messages en masse and sharing them with state authorities?
