I'm not sure I agree with the anecdote in your first paragraph, and indeed I preemptively addressed it in my comment: one's own experience is just one way in wh

I'm not sure I agree with the anecdote in your first paragraph, and indeed I preemptively addressed it in my comment: one's own experience is just one way in which something can be hard to learn, whereas people who are regularly teaching and interacting with beginners have a broader view on what people find hard. My experience is, broadly speaking, good teachers are those that have had a lot of practice teaching their material.