This is beautiful work, Tom
! I do like the sense of vastness in this painting - that sky is especially impressive. The mix of cloud types adds a real sense of reality. Your colors look fantastic too!
In regards to your dilemma, I can see why that would be an issue without the aerial perspective. One thing that might help give more depth is to sharpen the details in the foreground, perhaps more texture in the riverbank, a few tiny pebbles, and more details in the water's surface. Likewise, maybe a softening of the distant rock formations - less individual details and more soft forms. I don't think either of these changes have to be taken too far - it's already beautiful just as it is! Hope you'll share your finished painting with us.