All these points apply to PCs as well.
And while all-in-one integrated machines are popular, and tablets etc are taking on the low end of usage, the familiar modular PC is still massively useful and very necessary for a large part of the market. There are extra challenges in doing this in a mobile device, but none of what you said is a dealbreaker.
There has certainly been interest in modular phones, and while they will inevitably require tradeoffs, whether those are insurmountable or how much they reduce its potential market still remains to be seen. History has seen many cases where niche products have grown in popularity as their engineering gets refined. Personally I'm glad to see someone trying something very different, rather than just tiny refinements to what we already have.