I totally see where you are coming from. I had some of the same reservations initially, wondering about the accuracy of the theory. The fact that the theory book devoted so much time to the archetypes of the original Star Wars, which seemed spot on to me, helped pull me in. (I grew up playing Star Wars and happened to have a last name of Lucas, so it's kind of in my blood -- even though no relation to George my name was literally on all the toys!) Then as I got the software and started to apply Dramatica to my own work, I decided to put any doubts I had aside and just act as if I knew the theory was rock-solid. That may not be easy for everyone, but I think it's required to really progress with it; you can't work with tools you don't trust.
Anyway, by taking that approach it didn't take long before I became absolutely convinced in the accuracy of the theory and the effectiveness of using it in my writing. It may not be for everyone, but for me it has helped immensely. (The problem I had before was that I could not follow any other advice on narrative structure, they all seemed wrong or just like they didn't work for me. Heck, before I found Dramatica I was forcing myself to write about my main character's Lie and Wound, and Truth that she had to find, because I thought she had to Change. Except every time I would force myself to do that, I would literally feel sick to my stomach, and not know why. I thought it was because I wasn't cut out for writing this way with outlines and character sketches, that maybe I had to "pants" everything, but I knew that had never worked for me in the past. Then I found Dramatica and it made me realize that my MC is a Steadfast character! And suddenly once I had a storyform I became someone who could write oodles of stuff about the characters, really get into outlining the plot, etc. No more sick stomach.)
If you want to be convinced, go watch Zootopia and then (and only then -- you have to watch the movie first!) read the article analyzing it on narrative first. You will be utterly amazed at all the stuff that Dramatica predicts with so little input (all the red stuff in the screenshots is Dramatica's output, while blue is input). For example, while watching the movie pay attention to how the main character (Hopps) at one point is able to solve a major problem in the overall story through some silly ability she has (MC Unique Ability). Think about what realm that ability lies in, and then see what Dramatica says about it from the storyform. It seems incredible that it could predict that at all, let alone on so little input, but there you go.
NOTE: I just realized some of the screenshots are missing on that article, so you can't see the full red vs. blue domination*, but you can still get the gist. (*No, that is not a political statement, I live in Canada. )