It doesn't matter how proficient you are with your camera and how expert your post-processing skills might be, without a full and strong understanding of composition, you will likely fall short of great images, most of the time.
Composition was an area of photography that I found a little confusing at first. When I bought my first camera and researched it, it seemed really simple: generally just employ the rule of thirds. Then over the next year or so I began to learn of lots of different rules and requirements, to the point where I honestly couldn't figure out how to ever frame a photograph properly. While I don't do much landscape photography these days (outside of using drones), when I was a beginner I did and I found it frustrating. I remember trying to find foreground interest, put the horizon on the upper third of the image, find compelling elements in the scene, balance out the image, capture the light in a way that improved the image, and so on. It felt insurmountable.
These days I have condensed all that compositional noise into one rather simple rule and now, when I take any image regardless of genre, it's what I abide by: what keeps people looking at this image. Nigel Danson is a superb landscape photographer and educator, and in this video, he discusses this subject in a bit more depth as he was a judge in the World Landscape Photography competition.
What compositional rule is most important to you?