Composition is by far one of the most deceptively nuanced and difficult to master aspects of landscape photography, and one of the traps photographers frequently fall into is making their frames too busy. This excellent video discusses whether a scene can be too busy and what you can do to correct the issue if it is.
Coming to you from Gary Gough, this great video details the issue of busy scenes in landscape photography and what you can do to fix them. This is a common problem in the genre, and there are a few ways to fix it, the easiest being simply to zoom in and exclude more elements from the frame. This is why I think all landscape photographers should carry a telephoto lens in their bags (it can be a light and affordable f/4). Of course, this does not mean you have to let the pendulum swing to the other extreme and start shooting minimalist landscapes (though that is a wonderful style), as there is certainly a middle ground that suits the majority of compositions. Check out the video above for the full rundown from Gough.
And if you really want to dive into landscape photography, check out "Photographing The World 1: Landscape Photography and Post-Processing with Elia Locardi."