I like the human-relatable story behind it. I think many kids experience a similar situation that sparks this life lesson.

My younger self condemned my father's printer as "dumb" for printing a multi-page print job in reverse order. It took me a couple days to understand it does that so that you have them sorted once you pick them up (printed side was up). By that time I also have already publicly declared the stupidity of that printer. I think the shame after my enlightment deepened this life lesson.

Before calling something dumb, I try to come up with at least 1 answer to “Why would you do it that way”

Mostly stopped calling things dumb since I adopted that rule.

But very often the answer is "It saved some development effort, but not all that much." or "It saved a very small amount off the per-unit cost."

In those situations, "dumb" tends to be a correct judgement.