I agree with the tip to level out the horizon. A tilted horizon in this sort of composition will be entirely too distracting so thats a good fix.
With this particular subject, I may have used a shallower aperture (2.8 or 2). Especially in this case where the background isn't too flattering- the tree is awesome, and we really want to show this off. Not so much the powerlines or forest eh? If I could go back and shoot it again I would use a shallower aperture, perhaps wait for sunset (don't really know what direction you're facing here) to get some more dramatic clouds in the sky.
I like how you cropped it with the sky open at the top, this works well. I actually have a similar image, although its a night long exposure so it has a bit of a different vibe
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