So far I've not heard "this can't be done." All I've heard is "I don't know how this might be done." Huge difference there. I also hear a fair bit of "this shouldn't be done", which I find incredibly disappointing. Here's a hypothetical: we already know how to do noisy, shared-media device interconnects. It's called 802.11. Look at the size of wifi adapters: you can get a usable signal that works over meters from som…
Even perfectly functioning modular plugins take up extra space - a "classic" phone can instead either be smaller/thinner, or put in a bit extra battery in those cubicmillimetres; which both make the "same" phone better.
Modularity imposes a cost, it's a tradeoff - and even for laptops we're seeing that people tend to prefer a bit of size/weight/battery life rather than modularity.