> Wouldn't everyone just prefer a secure, modern texting app that could message literally anyone with a phone number? Without having them download a specific app? Then we could all text together without the headaches.

https://m.xkcd.com/927/

I’m not sure what messaging standard you propose gets adopted, because the flavour du jour of most non-iMessage users is RCS, which as an open standard, is unencrypted and insecure.