TLDR; Specifically this is about the last mile problem, not about opinion basis. Though I'll grant that opinion basis is related and perhaps implicit.
Note: I may be incorrect in my interpretation of what opinion based means. If so please correct me.
When the answers to a question are as varied as opinions, i.e. they represent various factors, then we fail to tune the question and answer process. So the process becomes about eliminating factors. Sometimes that may not be what we want to do.
The answers in this case seem to offer factors where as a specific reason is harder to pin down. Some kinds of questions seem to be simply like that and involve a lot of factors.
I understand we have resources on how to ask questions, that's not the point. The question is about human effort on both ends, moderation and for the OP.
So the specific question, demonstratively, is in two parts ( one that looks easier to answer, and one that looks harder ):
- how to detect when this happens
- how to approach resolving the number of factors more effectively
...in order to result in fewer answers, which may otherwise be useful, but less so when the list of them is longer on the same question?