Nobody forces you to use iMessage. Use Snap, Whatsapp, Telegram, FB messenger, whatever. You don't need to be upgrading with every cycle (or even every other cycle) either. I am on my 4th smartphone since 2008, replacing a battery is cheaper that replacing phones. And if your teen insists on the latest&greatest instead, that should be your problem, not Apple's.
Without their walled garden Apple is nothing but a commodity hardware maker and those do not survive for long on this side of the Pacific.