From LivingPianos.

https://livingpianos.com/what-is-the-most-important-finger-in-piano-playing/

Welcome to LivingPianos.com, I’m Robert Estrin. Today’s question is: What is the most important finger for playing the piano? Of course, all of your fingers are important, and they each play a vital role. Imagine playing the piano with less than ten fingers. It would be really hard! It’s hard enough with all ten fingers. But there’s one finger that really is pivotal for playing the piano. Not only that, but it is arguably the most important finger that you have for everything.