I See your point in not wasting time in something useless. Unfortunately I do not think that learning is useless. Ever.
Learning (a new skill, a new notion, a new procedure, a new recipe, etc.) expands our brain and our opportunities. Especially if you consider the huge possibilities that lateral thinking adds to learning a new skill.
Not to mention the pleasure one gathers from being able to do something new and, again, the opportunities that may arise from that notion.
So, no. Time spent learning is never wasted.