I kinda feel the same way. I loved slowly going through the main story and probably put 50hr into the game, but the sandbox alone (amazing as it is) just doesn't do it for me.

The issue I have with stacked PRs isn't merging, but rather, when I change branch A, and I'm working on branch C, I then need to merge A into B and then B into C just to continue working. Collapsing/merging them at the end is the easy part.