If everyone's messaging has to be compatible with everyone else's then maybe we will finally only need one messaging app on our phones again instead of 5. Sounds great. I just want to be able to send messages without thinking about which app I need to go into to communicate with a particular person; that really breaks my flow when I'm trying to get something done. I don't give a shit about any features apart from pic…
You don't care about any features, apart from the features you care about. Just like everyone else.
That's a pretty uncharitable way to interpret the statement, when the three features OP mentioned are a part of literally every modern messaging platform that people use. Not just iMessage and RCS (the open protocol which is the best analog to iMessage), but WhatsApp, Signal, Telegram, Discord, Messenger, Instagram, Slack... It's actually hard to think of one that doesn't. I guess IRC, if you consider that in any way comparable to the others, but it really isn't at this point, being a now fairly obscure protocol reserved mostly for tech-savvy people and niche cases.