Welcome to science! In 10 years, a lot of what we believe today will be somehow invalid bullshit!
Say it with me: current theory suggests....
I'm an engineer. When the entire field of cognitive science rolled over on its back for K. Anders Ericsson, I said, alright, the research is funny, but the conclusions are useful. So it's all fucked up, full of bullshit and misunderstood data. Ericsson's hundreds of papers and books all boil down to one thing: experts become experts by a principle he calls "deliberate practice", whereby a person must have goal-oriented, technique-focused practice strategies with constant and immediate feedback. Cognitive scientists now define "practice" as some sort of activity that GENERATES ERRORS, having decided you don't learn if you're not fucking it up.
So maybe they don't understand all this bullshit; but they understand now that the prior theory--10,000 hours of rote mechanical behavior to become skilled in something--was bullshit. As an engineer, I don't care that the new theory is full of holes; all I care about is they definitely know that time doesn't really correlate with expertise, except by the confounding of more types of activities occurring in longer time. If you've done something for 10 years, you'll have made and corrected for more mistakes in your career as if you've done it for 10 minutes. The new theory? You have to pick a technical facet of the skill, practice that directly, and do so in a manner that strains your abilities and forces you to make mistakes you can learn from. I'm on board with that, because it works; at least, it works better.
In 10, 20, 50, 100 years, they'll come out and say, hey, we figured out you're like 5 times more effective if you practice in this way, and that whole "deliberate practice" pseudotheory bullshit was just missing this key common behavior among practitioners of deliberate practice! I'll be like, hey, that's cool, we'll do that then, because it works better.
Current theory suggests playing complex songs you can already play on the piano day after day won't make you any better; playing difficult songs will make you better very slowly; and determining what piano musicmanship skills you're weak in and drilling them directly in a fashion demanding skill beyond yours such that you make mistakes of a nature you are able to identify and correct for *will* advance your skill *very* quickly. Maybe current theory is full of bullshit, but all of these statements are verifiable as true, and so I know how I'm practicing my skills.