​How do you become a better piano player? Like most things in life, it's a simple question but complex answer. 

You want to "reverse-engineer" the solution. First, figure out what type of piano player do you want to be. For instance, do you want to be a solo pianist? Collaborative Artist? Accompanist? Jazz pianist? Choir Accompanist?

There are many different paths to piano, but once you figure out which  road to go down then you can begin to practice the particular skill sets that are necessary for that specific choice.

Watch this video to find out. But lastly, two core skills I think you need no matter what is 1. Technique (Mechanics) and 2. Playing by ear (Improvisation, etc.).