I think introducing some sort of "cost on giving opinion" could work. You get to ask a question if and only if you also provide some sort of solution to the pro

I think introducing some sort of "cost on giving opinion" could work. You get to ask a question if and only if you also provide some sort of solution to the problem as stated by OP. The opposite equals downvote. Also, as Taleb says "be wary on anyone giving you advice which you didn't ask for".