It's as simple as that to play the piano. Just sit down and do it. So what is a teacher for?
Great question. There are tricks to using one's hands fluidly and without consciously having to control their every tiny response.
One of my students has no actual technique except for responses to his extremely accurate ear. I watch him adjust fingering and touch in the tiniest increments to match balances that he hears coming through Beethoven's line. It is extraordinary to watch. His goal is not to slam through the piece as if he knows what he is doing, but rather to know what he is doing.
And does he ever! I could pay attention to that kind of responsiveness all day. And I mostly do, the only exceptions being when I chance upon commercially mangle-ironed samenesses (purposeful plural)coming at me over the media.