To be successful in piano, you need to repeat stuff. Again, and again, and again. There's no way around it.
If I had to pick one reason students don't improve, it's this: Taking small bits of music and repeating them 5-10 times without errors is too tedious.
But, here's the irony.
Not following this repetitive practice process results in students taking 2-3 months to learn a piece of music. A piece of music that could have been learned in a week or two with proper repetitive practice.
Repetition isn't everything, of course. One can only do this sort of practice for short, focused sprints at a time.
But, it's essential for myelination to take place in the body.
You know, that biological process that makes things automatic. Like playing a piece of music fluently.
To kick it up a notch, I would also argue that most successful people are obsessive about repetition. Repetitive practice. Repetitive about showing up every day. Repetitive in thought patterns.
Most people aren't willing to engage in repetitive practice. But the ones who do are the ones who master their craft.
Whatever that may be, in music or in life.