I’d say this is evidence that Dramatica isn’t very popular among novelists, not that it’s not helpful. Success on the level of King/Patterson/Grisham is extremely rare, so multiply that by the small percentage of novelists who’ve taken the time to study and use Dramatica properly, and you arrive at a low likelihood that any of them use it. (Plus, once you’re capable of writing bestsellers without Dramatica, it’s unlikely you’ll bother taking the time to learn such a complex theory.)
But there are at least a couple of very successful novelists on this very forum using Dramatica. @pattyloof is a bestselling author. And this post by bestselling Hugo-nominated novelist Sebastien de Castell is really great:
Perhaps a better way to evaluate Dramatica would be, ask yourself if you feel it’s helping you make your stories better. Does it help you to fill in gaps or correct things that don’t feel right?
I agree it’s not easy to apply Dramatica properly to the writing process. Sometimes I think using the entire storyform (all the story points) might be trying to do too much consciously, when a lot of that stuff is better handled subconsciously, at least for some writers. However, I do think having a strong grasp of the four throughlines would be helpful for almost anyone.
I wonder if you could clarify your question around what part you need help with “believing”. Do you already believe that the analysis side of Dramatica works, and just need help accepting whether it can be applied to the writing process?