I credit JWN with helping me to sort out my conflicting beliefs after I left the JWs. It took me eight years to get over the mind control that made me fear so called "apostate" sites, then another few before I could say I no longer believed in God. It was a life changer for me, I no longer feared the wrath of an angry God for not knowing which of the many religions that claimed to represent him were the ones he approved. I didn't post on those threads because the ones who did made a better argument that I could have, but I read them and learned.
So yes, many people view these threads, but don't post, but just because the ones who post as believers don't lose their belief in God, it doesn't mean such discussions are futile, on the contrary, I think they are very important.