I like it when there is a core theme or building block. It makes an art very attractive, mentally. It’s easier to remember things and relate them back to that core thing. You can keep coming back to circle walking or san ti shi, or zhan zhuang and shi li, or the snake move. There is some built-in good solo practice because of the relative simplicity and there is a way to retain that style’s flavor and approach, build on it, and come back to it. Most arts don’t seem to have that as much as ba gua, xingyi, yiquan, and bjj seem to. I’m not really sure but I’ve tried to learn taijiquan for decades on and off and maybe that’s part of my learning problem. Things don’t boil down to that one core thing, at least in my mind. One can say “always yield” I suppose, but I don’t see that really being the same thing and I don’t really think that’s “it” anyway. It’s also vague and applies to any soft style.