>I'm confused by the discussion of OO

I don't think anyone's saying you can't do it without OO. Just that existing popular patterns for UI tend to rely on OO patterns like inheritance and classes with instances, and easy-ish namespacing and ownership concepts that map to those ideas.

So doing it without OO is harder, as it requires something different, that may be studied, but is less well explored and documented to the average person.

I recall similar discussions about doing UIs in C. GTK, for example, sort of fakes OO in C, I assume for related reasons.