This is weirdly only a thing in America. In Europe, where I live, iMessage isn’t that popular and iPhone users never seem to care about the bubble colour (likely because WhatsApp, Telegram, Signal, Element, and Threema are so popular, everyone is used to using multiple chat apps anyway).
Edit: Also I’m not sure why everyone is championing RCS - it’s yet another proprietary communication standard like iMessage and isn’t open thus can’t be easily implemented in other chat apps.
Rather then pressure Apple to support and further popularise another closed protocol, we should be pushing for something open like Matrix or Signal.