Those other new things are new and different, and it doesn't mean that they should change existing basic built-in functions. In fact they haven't even really done that as the camera icon button is still there, but they took essentially half of its functionality and moved it somewhere else.Yes...that’s where the disconnect is with this.
Before, all we had was attaching/taking pics in iMessage.
But now I can do HUNDREDS of other things through iMessage. The fact that you (or even I) don’t use it to its full extent yet, doesn’t mean it is t needed and a good change.
I do now find myself using it for Animoji (just upgraded to an XsMax from a 7+), using the GIF apps more now, sending songs with iTunes button, etc.
Old habits die hard...that’s all this is...not bad design or adding stuff that isn’t needed.
There can very well be reasoning that could be used to explain the change, but that in itself doesn't mean that there aren't reasons for the previously established way working out better for plenty of users.