Squinting makes the subtle variations in value and color disappear. The wrinkles are smoothed out, leaving simpler shapes of light and dark. The image looks more like the version below.
This would be a very useful preliminary study of the image. It reveals the basic structure in a form that is not distractingly complex. Seeing the dark/light pattern so clearly makes it easy to know where you might want to adjust the composition. That dark patch in the lower right, for example, is too distinctly vertical. It looks like another trunk. I'd rough up its edges a bit.
Most likely, the squint version looks too simple to you, but that's exactly the idea of a study. It's supposed to be a rough draft. A proper painting probably doesn't need all the texture you can see with your eyes wide open. Removing most of the information allows you to add a little subtlety at a time, increasing the odds that you'll find the right place to stop.
Here are a couple more images that benefit from squinting:
Make a deliberately over-simplified study that emphasizes the shapes and lets go of the texture. Where you see adjacent shapes of similar value, consolidate them, making fewer shapes overall. Stand back from the finished study and ask where you'd like more subtlety or specificity. Take notes. You may want to make another quick study with a little texture added. Proceed incrementally, remembering that it's better to err on the side of too little information than too much. Take notes, and move on to the proper painting with increased clarity and confidence.