The thing is, Samsung DEX works great but I've never met anyone who has heard of it even among people who have owned nothing but Samsung phones forever. Samsung just sucks at advertising the feature. They should sell a bundle of phone + portable USB-C screen + Bluetooth mouse and keyboard and the thing would sell pretty well I would imagine. But right now no one even knows this exists.

The product is perfectly fine as it is. The way I see it, if it's being advertised, it's being monetized behind the scenes. That changes incentives and usually makes the product experience worse. All it has to be is a window manager that supports standard desktop KB shortcuts (CTRL-C, ALT+Tab, etc.)

I also think a lot of people actually prefer having a separation of devices.