Tell us this, how many different aspect ratios do you have in your portfolio?
You seem to assume that people who compose inside a given frame do so because they don't understand how composition should work, and don't know that it could be done another way.
Composition is not about a frame dictating how you arrange things inside it, but you dictating how things are arranged inside that frame. The world is not full of ready-founds, objects that have a natural frame around them. We do that to those objects. We arrange them inside a frame, any frame, such that it looks good.
You see, that's called creativity.
Excellent. I can see we're in 100% agreement. And "Darn", I was looking for a good argument. ;-)