The point is that iPhone users try to use 
    iMessage, and right now apple's weird SMS 
    integration with it makes them accidentally 
    use SMS and get annoyed.

I disagree that the "annoyed" people are "trying to use iMessage." I think they're just trying to message their friends. They are annoyed because the only common protocol supported by all parties in the conversation kind of sucks sometimes.

Apple has made the correct set of trade offs. If you just want to send a text message and don't care about the particulars you can do that and you'll automagically get the best possible experience based on the best lowest common denominator protocol whether it is iMessage, RCS, or SMS.

And if you and your buddies are savvy enough to want more than that you can install Signal or Whatsapp or whatever.

But that baseline out-of-the-box experience for mobile phones has always been "if I have somebody's number I can text/call them using my phone's out-of-the-box functionality and the network sorts out the details."

I think it's kind of nuts to throw that in the trash and you don't appreciate what a huge step backwards that would be for most of the people who buy and use phones.

Also, would you not agree that out of the box E2EE is a huge deal!?

But the keys and key exchange protocol for E2EE have to be managed by somebody. Signal, Google, Apple, whoever.