I’ve never had an instrument lesson in my life, but what you say about college lectures really resonates with me. I would dutifully take notes, then dump them in the bin on the way out. Maybe the act of writing them was helpful, but I never used the notes I bothered to keep as a revision aid.

Now I wish I had had the foresight to do what you did - and listen, empty-handed. What opportunities I missed! Too busy doing the dutiful thing to consider the longer-term. I think that that keeping a focus on a *good* speaker is possible for longer, but maybe it, in itself, takes training?