Exact. Same. Issue. All their solutions do not work. I've reset Apple ID and wiped all my old iOS devices. Roughly 90% of my friends cannot text me anymore.
What's comical about this is how easy it is to fix: have a cache that breaks weekly; upon new text message, ping Apple HQ and see if device is iOS and has iMessage installed; great, save for a week.
You can do better than that. User marks iMessage account as 'inactive'. Next time someone tries to send to his address via iMessage, ping their client with an "invalidate-cache-and-send-as-SMS" status code, and it's done. Everything is handled transparently to the sending user.
No matter what, it would require some sort of update.
What's comical about this is how easy it is to fix: have a cache that breaks weekly; upon new text message, ping Apple HQ and see if device is iOS and has iMessage installed; great, save for a week.