Composition is confusing at first, then it appears incredibly easy. But, once the basics have been mastered, the composition rabbit hole goes much deeper.
I remember when I first started learning about composition. I had no background in the arts or art history and knew no photographers or artists. So, the information was being delivered to me without a foundation. Despite how long ago that was, I remember how I felt: confused. It wasn't that the rules were difficult to understand, or the compositions of people's photos were hard to spot once you knew some of the most common rules, like the Rule of Thirds. My problem was how you ever shot something which was abiding by these rules, and how did you know which to choose? I remember trying to force compositions for every shot I took and find it deeply unsatisfying.
Then, gradually I learned to see the world with grids on my eyes, and the whole concept felt simple and easily applied. The issue is, if you try to stick rigidly to these rules, you're missing a few things. Firstly, you're missing the many creative compositions that don't perfectly map to rules, and those can often separate images from the pack. But moreover, you're often neglecting the whole point of these compositional rules in the first place: keeping people looking at your image.
In this video, Karl Taylor goes through what he believes is the most important aspect of composition.