This is purely a UX issue, and there's no particular reason why iOS would even need to be more open to rectify it. They just need to improve the UX.
But, more broadly, the problem is that they can do it for their own apps, but for all the third party ones, it's down to app developers whether they want to put in effort to support keyboard & mouse/trackpad properly. And it's a chicken and egg thing there - relatively few users use it currently, so there's little motivation to add support, which deters more potential users.
Yes you are correct on both accounts. The problem is two different OS approach. What I need is an iPad hardware running macOS actially, with a tablet mode. Same issue with Chrome OS/Android separation.
Funnily enough Windows is the closest to get this right with 2-in-1 tablet/laptops. 2 problems with this: 1- Windows, 2- sub-par HW.
But, more broadly, the problem is that they can do it for their own apps, but for all the third party ones, it's down to app developers whether they want to put in effort to support keyboard & mouse/trackpad properly. And it's a chicken and egg thing there - relatively few users use it currently, so there's little motivation to add support, which deters more potential users.