Informed Simplicity is an enlightened view of reality. It is founded on ability to discern or create clarifying patterns with complex mixtures. Pattern recognition is a crucial skill for an architect, who must create a highly ordered building amid many competing and frequently nebulous design considerations.~ Matthew Frederick from, https://fs.blog/2016/06/three-levels-knowing/
As you’ve no doubt discovered, getting to the level of informed simpicity is difficult. It requires deep understanding of a field, and that requires significant time investment. In my opinion, a hallmarks of subject mastery is demonstrating a level of understanding that reaches informed simplicity.
If I think something is simple, either I’m a beginner or the subject isn’t complex enough to be a mastery practice. If I think something is complex, then I know I’m a beginner. And if when asked about the subject, I find myself looking up a little with my eyes, while making that lopsided, slight smile… suddenly lost in thought? Then I know things are getting easy.