MS text messaging is an archaic, expensive, and limited messaging standard. Yet it remains in place as the de facto standard for notifications because everything else is a walled garden and cut off from other messenger services. WhatsApp does not send to Telegram which does not send to Signal, etc.
Apple has deliberately withheld iMessage from non-iOS platforms, so that has never been considered as an option. To replace SMS though, the messaging has to be baked into the phone OS (not to be voluntarily installed or uninstalled by a user), and this is where the RCS standard came in, which also needed mobile carrier support. As it stands, RCS has been adopted by most major carriers and Android devices... but it has zero penetration on iOS because Apple won't adopt it.
It's time Apple faced up to this and sat around the table with the other players to discuss a solution that benefits all users. We can't move on from SMS unless there is a proper alternative that is fully adopted.
See Google exec gives harshest rebuke yet of iMessage lock-in effect in push for RCS on iOS
In recent years, Google has been very critical of Apple not supporting the RCS standard to make iMessage more interoperable with Android...