Which is more challenging: understanding art theory or improving artistic skills?

For me?

Improving artistic skills is far more difficult.

Art theory is an academic pursuit, which, while challenging, is nothing more than an intellectual enterprise, no big deal for me.

Actual artistic skill requires something I do not excel at, practice. As a physical skill, the only way to acquire them is repeated, correct, practice. Incorrect practice only reinforces the mistakes. Therefore one must start slowly, getting each move correct before progressing to the next, going back to the beginning and repeating until one can go from beginning to the end of the series flawlessly. Then begin speeding up as muscle memory forms. It is the same whether the skill is painting, sculpting, music, or dance. Poetry or prose. Whether the muscle is physical or mental. One must begin at the beginning and and slowly progress until mastery forms. Approximately 10,000 hours of practice should suffice.