You're so focused on trying to come up with reasons why I'm wrong that you're missing the forest for the trees. I (a single software developer) spent a whopping 5 minutes thinking about this problem to come up with a fairly reasonable hypothetical solution that would solve the vast majority of complaint that people have with MMS group chats within Apple Messages. TimFL1 just posted that Apple did indeed implement at least 1 of the things I hypothetically suggested:
Send high quality media to iMessage capable user, the rest get crap. Nothing about the situation has fundamentally changed recently that makes that possible. It has been possible for many, many years. Apple simply CHOSE not to do them. With their army of developers, they likely could have long ago alleviated most or all the problems with messaging when non-iMessage users are part of the chat. Claiming that Apple has played no part in the current messaging mess and it's entirely the rest of the world's fault is equivalent to sticking you fingers in your ears and singing la la la, because you don't want to acknowledge the facts.