A question can not be “dumb”, “stupid”, or in general bad. That is conceptually and technically contradictory to state.
Stupidity (or equivalently dumbness) may exist in behavior or in a statement, where an incoherent and inconsistent conclusion from a set of prior knowledge, or such judgements having a set of prior knowledge, exists. Another word, knowledge comes first, stupidity could potentially come next. Reversing this process is technically problematic.
Purpose of a question by design is to seek knowledge. Not unless seeking the knowledge is regarded a questionable act, calling merely such pursuits dumb is by itself incoherent, inconsistent, and may well be called “dumb”.