> 1. No threading is supported. If you reply, it duplicates the message being replied to.
Threading (using "Reply") is not supported in mixed iMessage/SMS/MMS text chains. (I'm using iOS 16, so this may have been (unwisely) supported in earlier Message versions.)
> 2. “Tapbacks” (reactions) duplicate the message being reacted to with “so-and-so likes message … message”
You can now see iPhone tapbacks on Android phones in Google Messages. I'm not sure if it's on defaultly yet. https://www.macworld.com/article/610908/google-messages-andr...
The other things you list are limitations and side-effects of the standards used. They're valid, but I consider the experience "fine" without them. If the groups I text with cared about these we would probably use WhatsApp since everyone has that. Signal would be my preference, but it's hard to change people's habits.