Piece of feedback I recently spotted in the wild, paraphrased:
You should have done X. X is easy to do.
It’s only easy once you know how to do it!
It reminded me of a tweet from @jessamyn about helping someone with a piece of technology: “Simple stuff, hard if you don’t know it” and her post on Phil Agre’s 1996 advice on helping others to learn computers: https://www.librarian.net/stax/4965/how-to-help-someone-use-a-computer-by-phil-agre/