Those are all closed-loop messaging systems. If anything whatsapp/imessage/whatever are more vulnerable to what was suggested because they aren't open/standardized protocols.
SMS is an insecure protocol from the ground up it was never designed for the mass communications it is now used for.
It is open, sure but it needs a new open standard to completely replace it, which will take decades because its used for machine-to-machine communication in US telecom infrastructure and the sheer amount of physical equipment that would need upgraded is insane.