As written in my title, I wanna ask an opinionated question on Math.SE, but I am not sure if this is okay. So I have this kind of meta-question.
Technically, yes, you can. Whether or not it will get closed very quickly, amass downvotes, deletion votes, and ultimately be weighed against you when the time comes to face the algorithm's decision to limit your questions, as well as possible suspensions if you keep creating these sort of discussions... well, that's up to you.
This is a common mistake, calling this site a forum. Forums are meant to facilitate discussion. This is a Q&A site, it is meant to have questions and answers to these questions. Yes, we have the comments where we can have a modicum of discussion, but those are really meant like salt and pepper: it's not the main course, it's just something to flavour your meal.