Not sure if this has already been brought up here, but I personally define trivial questions as the type of questions that make me ask myself "who cares?" If the information does not solve a problem, or the problem it solves is extremely niche, then I don't see the point in having it on the site. Questions that don't solve a problem would be things like, "What are all of the Pokemon that learn a Normal type move on level 32?" I know that's at least a bit of an exaggeration, I know that we have gotten questions that ask for information that is just as useful (which is not very, if at all) as the information the aforementioned question asks for. If the reason for asking a question seems to be "just because" instead of "this information is useful to me/may be useful to other people," then I think we should get rid of them.
As for what I'd define as a "niche problem," I believe that these are questions that ask for information that solves a problem unique to one person, such as "What are all of the Pokemon that evolve on [level]?" in the context that the person asking is making a list of Pokemon sorted by what level they evolve on. I personally feel like this also constitutes as a trivial question. The information it asks for can't be applied to any other situation that has any use, at least, as far as I can think of, and, on top of that, the information it requests isn't something that someone can obtain just by going to two or three Bulbapedia pages, (I'm assuming Bulbapedia doesn't have a page that has all of the Pokemon and the levels they evolve on them, but, if there is one, then pretend it doesn't exist for this example) it's something that would require going to the Bulbapedia page for a Pokemon from every evolutionary family.
Basically, what I'm trying to say is that when there's a question like this, whether or not it says up should depend on how useful the information it asks for is, how easily the information can be obtained, and the amount of time it would take to do so. I feel like a timeframe would help us measure this. I feel like after a week or so, if the question hasn't been answered, or doesn't have any discussion regarding interest in the information/comments working towards a complete answer, that means that nobody is willing to put in the effort and time to answer the question, so it's not something we should keep up.