First of all, when Apple created iMessage, there was no possible way for them to predict that friend groups would use it as a reason to treat members of their groups poorly due to using Android phones.
Second of all, Apple did not deliberately make interacting with non-iMessage users in group chats "look like trash" in order to exclude them. Apple went out of its way to make it possible for iMessage to interoperate with the ubiquitous (in the US) SMS, with reduced features because SMS did not support the better features. If, instead, Apple had just made iMessage not interoperate with SMS at all, you'd be screaming about that instead.
Third of all, if people are leaving others out of chats, that's not Apple's fault. That's something for those families and friend groups to work out amongst themselves. "Hey, guys, I don't have an iPhone, and don't really have the money to get one, so maybe we could use GroupMe/GChat/WhatsApp/Signal/IRC/email/smoke signals/meeting in person/any of the myriad other ways of communicating instead?" A) "Oh, sure, that shouldn't be a problem!" (everything is solved) B) "What? No, we're not going to change anything just because it makes it impossible to actually include you in stuff. That's a you problem!" (turns out, the problem is your friends are assholes)
Apple cannot by any reasonable standard be held to blame for the way bullying, status-seeking teenagers treat each other.