Yes.
Do you have anything to base this answer on?
Of course it's possible. Didn't Richter start the piano at like age 20 or something?
He was self-taught since like 10 when he started taking piano lessons in his early 20s, actually.But yeah, on topic, this is kind of a tricky question.Honestly, do you want to know the only difference that's (more than likely) going to show?Recognition.IF you are talented enough, at the moment you'll reach the technical skills required to participate in international competitions, you will be too old. And almost every renowned concertist admits that, nowadays, winning competitions is pretty much the only way of getting recognition and earning your life as a non-teacher professional pianist.I am not saying it's too late, don't get me wrong, you can reach an outstanding level even if your start in your late teens, just as good as any pianist whose childhood as been dedicated to practice, but you'll simply reach it later. If your goal is not to make a living out of it, than obviously, go ahead, nothing stops you really.
Some flaws in your argument I had to point out. There is a difference between winning a competition and truly being a concert musician. Sure competition winners are really good, but in order to go on to a truly successful career, you need more than that. I mean seriously if you look at the list of Tchaikovsky and Chopin competition winners, you will see that you will not recognize several of them. That is the thing with competition winners. They win, they play for a few years then are forgotten. I was once told that you know how well you play by how well you can play Schubert and Beethoven Sonatas past the age 35.And another thing, you seem to assume technique is what makes concert pianists. While technique is a big issue for students, once you get too old for competitions, technique should be the LAST thing you should be worrying out. Musical communication and maturity is what makes music difficult. Not technique.
I just want to reach the technical level to be able to to justice to pieces like Chopin's ballades.. I started playing when I was like 14/15 years old, my goal is not to become a concert pianist, but as good as possible And I want to be able to play the ballades, the etudes, appassionata and pieces like that... Is it possible?