If you think that great photographers always produce great images and never have problems with mediocre or even bad photos, then you are mistaken.
The best photographers in the world take bad photos, they just NEVER show you them.
In regards to landscape photography a good photographer will make sure to try different compositions and angles to capture the scene in front of the camera. It may take a long time to set up the camera and have all the right settings for the scene, but this doesn't mean that the image will be prefect.
For example I recently went to photograph the Samuel Beckett Bridge, over the River Liffey in Dublin. I chose three different angles to try to capture the bridge. For each of these angles I tried different compositions, more of the sky in frame and less water or the reverse, having the top of the bridge in the right, centre and left of the composition, etc. Then I tried different settings to add the atmosphere I was looking to capture, slowing the shutter speed so that the water started to look smooth, adjusting the amount of contrast in the shadows, etc. It took me about 1 - 1.5 hours to get everything I needed.
Then when I started editing them on my computer I soon realised that one of the angles I had chosen was not what I was hoping for. It really didn't work. I had the image I wanted with one of the other angles so I continued with these shots and produced the final photograph that I was very happy with. Now I didn't show anyone the shots I wasn't happy with, only the one I was.
Being selective is the first thing photographers will do when starting to edit their photos.
Samuel Beckett Bridge - the photograph I was happy with
The photograph I wasn't happy with...