SMS is simply the lowest common denominator. If you want to send someone information given a phone number, SMS will work. That isn't true of iMessage, Google Messages or even RCS. Any method other than SMS or a phone call, requires more information than just the phone number.
That's not true. With just a phone number I can send an iMessage. Their number turns blue when I type it in letting me know that they have an iPhone. This type of support could easily be added for Android, which would cover most use cases.
My point is you're right no replacement exists today, but the technology does and could easily be expanded if the phone companies agreed to phase out SMS.
Just because apple has a terrible system doesn't mean the rest of us should suffer.
Of course the technology exist, it's not like sms is some marvel that humanity could never reproduce. It is just that noone has the right incentives to do it properly or with users interest in mind.
