The following is written without any particular photographer in mind. It's based on years of looking at gallery walls, seeing people's prints at workshops and online, and going through hundreds of websites. I'm afraid it might come across as 'holier than thou' but is meant only in a helpful way. Each of us struggles with the issues mentioned to some degree or other.
I look at a lot of photographs. Some are by near beginners, others by people in the hobby for 30+ years. Quality ranges widely and some are fantastic, yet a fair number of the images are quite week (even by the same photographer as the great images), more often lacking aesthetically rather than technically. The images have no message and are often just a hodge podge of pretty things thrown together in the image. I've written about the finer points of creating images, but these shots are failing at a fairly fundamental level and at the risk of offending, I think it's important to deal with this issue.
These images fail, not because someone did or didn't use the rule of thirds for composing. Rather they fail because the photograph is a disorganized jumble - bright sky here, deep shade there, branches sticking out everywhere, somehow I have the impression that what the photographer saw isn't what ended up in the print. Giving advice on improving the image is difficult - telling someone I wouldn't have taken the picture at all isn't terribly helpful yet it's true - the image doesn't need improving, it needs replacing. Unfortunately the photographers are often unaware of their faults or if they see something lacking, are convinced that it could be fixed by a better camera, more pixels or some technical fix the experts have and aren't willing to share.
The following are a list of the more common reasons for images to fail. Since lots of my old images, and not a few of my current ones fail for exactly the same reasons, I hope you'll forgive me for raising the subject and for suggesting some image faults to avoid.
1) the image is confused because when you saw the scene you did so in three dimensions with two eyes, the viewfinder not withstanding. There are various ways to fix this - oddly, looking through an slr viewfinder isn't one of them - better is direct looking at ground glass, even better if it's upside down, but a framing rectangle, viewing filter, large screen digicam or even a rectangle with your fingers with one eye closed are all better. The SLR viewfinder with it's dark surround and optics making the image appear at distance and the relatively small size of the image all contribute to making the image look better than it really is.
2) you are photographing less than what you experienced - the image can't give us the sound of flowing water or the sigh of wind in the trees, the smell of new buds or the warmth of the sun on our skin. Nor can it record the emotions you experienced in this location - you're going to have to work to put any of that into the image and the image has to be strong enough to survive the removal of all those things - thus you have to be REALLY selective.
3) Something captures your interest but you can't find (or don't look) for a way to isolate it and a cluttered foreground or background completely spoils the image. It can be hard work to find a simple background and not infrequently you have to walk away - yes, the rock was interesting, but in it's current location it just doesn't make a picture.
4) Good photographs are NOT about cramming in as many interesting shapes and textures and other things into an image as you can. Even if adding a particular element could potentially add to an image, if it comes with excess baggage, it can do more harm than good - adding that sand dune to the left is good, taking the bush that comes with it is bad - short of removing things in Photoshop, adding the sand dune may hurt more than it helps.
5) Not enough effort has been expended to remove extraneous elements. Simplify, simplify, simplify. Clean up that image by moving to the absolutely best vantage point and do remember that knees bend - get low, wet and dirty if need be to get a good shot. You can remove extraneous elements by framing so they aren't included or they are hidden behind something or your position minimizes their prominence. You can reduce their effect by placing them in shadow, or make them significantly out of focus.
6) People include skies when it doesn't add to the image. Skies being bright and horizons often horizontal(who'd have thought), they really are a strong part of the image - for better or worse. I think you need to ask yourself not whether this time you should crop out the sky, rather you need to reverse things and ask yourself permission to use a sky because it's really important to the image. A travel brochure needs the horizon in the image, fine art does not. Should you feel the sky is important, do just about anything to break up that horizontal line of the horizon.