Traditionally, questions that result in answers containing a list of ideas have been off-topic, kindof...
Worldbuilding.SE has had a love/hate relationship with the "Primarily opinion-based" VTC reason. Part of the problem is that we deal with creativity and fiction, and so there's always some opinion involved. Worse, POB is meant to identify a failure to meet Stack Exchange rules requiring one accepted answer, so from our perspective, a question is POB is, in our opinion, you (the questioner) cannot clearly decide between the value of any two answers — which makes us mind-readers of a sort.
This problem appears to have come to a head back in 2014 where two of our most prominent members introduced VTC reasons that specifically forbade questions asking for lists of things as answers, such as a list of names. Both users proposed, had accepted, and deleted the same VTC reason on the same day. It was a whirlwind romance.
Unfortunately, list of things answers are actually quite common on worldbuilding.SE. How would X change Y questions almost always end up with a list of bullet points.
So, should they really be off-topic?
Over at English.SE they have a problem. People regularly ask "what's a word than means X?" It's not simply asking for synonyms (that gets downvoted hard as not enough research), it's asking, what's a single word that reflects this phrase/context/behavior/explanation/etc? They do keep the OP on their toes and are very quick to downvote (not close) if the question isn't clear (expresses exactly the meaning the word is meant to convey). THe goal is to produce a question that results in, perhaps, a dozen answers ... not hundreds.
And answers can only have ONE response. No lists. While I'm sure you can find exceptions sprinkled throughout English.SE, they're pretty good about this behavior. This is how they maintain SE's "one right answer" context. The answers must also be properly formatted: the word, its definition, and an optional brief description of why the word would be best, such that the OP can fully understand their choices and ultimately accept one answer.
There are two kinds of list questions
There are the obvious worldbuilding list questions like, what are the different kinds of clouds? What are the different kinds of political structures? Etc. These kinds of questions are usually quite definitive (meaning the length of the list isn't infinite and therefore POB). Therefore, these should be on-topic but downvoted if they demonstrate poor research (aka, you could have found that in 30 sec. with a google search and here's a link to prove it).
The other kind of list question results in an infinite list (one recently asked question was looking for a list of "trickster" styled names for magic users). While it may be true that there are only so many synonyms or perturbations of "trickster" to be had, the fact is that the list is open-ended. This, at the moment, is off-topic as POB.
Let's make "Infinite List" questions on-topic. After all, the purpose of this site is to help people build worlds, and sometimes what you need is some ideas. However, let's follow the English.SE model: answers can contain only ONE proposal and must include a description of why it's a good choice. Questions that are poorly contained (the "trickster" question is a good example of a good question under this context, btw) get downvoted. Answers that just give a word ("illusionist") are also downvoted as a handslap to remind answerers of their obligation to justify their answer.
It'll take a while to get everybody into the swing of things, but it would produce a meaningful solution to a common problem.