What am i building a frigging spaceship or a screenplay?

So many of my friends know that this is the 8th draft of this story. A few of them have even read every draft and are amazed (read annoyed) that each draft is a completely different movie. My main problem is that I don't do enough planning up front so the third act isn't as exciting or satisfying as it could be.

Hopefully, I'll be avoiding all of that in this draft because I'm spending so much time up front working on the structure and the plot twists, but why is this shit so hard? I think I'm making it harder than it needs to be....