Isn't it obvious that most of the problem is when people learn GUI procedurally? Rather than learning the GUI concept and visual language? Yes, the visual language changes somewhat, but not dramatically (a little flatter, etc).
Accessibility is important, but it pertains to issues of icon size, readability. Sanity of UI matters too (whether normal workflow requires a lot of click-sequences). But the main issue here is that no one should ever use a computer procedurally. Letting them do so may seem effective, but none of our systems are appliance-like (in the sense of fixed-function/interface). Yes, if someone only ever uses a computer for one thing, it may seem pointless to explain the concept of GUIs, but it's also necessary.