You lose a lot more than just message bubble colors when you switch away from iMessage. Multimedia quality takes a nosedive to 2006, reactions don't work, you lose encryption (SMS/MMS is not encrypted at all), and you miss out on all the other little things that make people like iMessage.
Of course this isn't really Apple's fault, we can blame the cell carriers for being categorically uninterested in modernizing SMS or making it secure.