It was announced in 2010 and then a year later Jobs died so it’s not out the realm of possibilities that other Execs decided against it and backtracked on it. It’s very possible if he lived longer it would have happened or at least an App would have released for it on Android and possibly iMessage would have had one too.
Who said the backup needs to be insecure?
You can literally encrypt the backup itself and use a pass phrase for unlocks. WhatsApp already does just that. Also WhatsApp uses Signals encryption and last time it was audited it passed with flying colours.
It’s possible they can push an update that would do client side scanning of messages while typed or that have been sent but this would be trivial to find out about and has never been reported on.
RCS is less “modern” or at least feature full compared to iMessage or at least was last I checked which was last year at some point. Group chats weren’t encrypted is a big one and it doesn’t interact with other apps the way iMessage can with apple wallet etc
Lol good luck finding new mods that will be any good after pulling a stunt like that. They certainly aren’t going to pay for any either.