EDIT: Oh and I know of at least one person who started playing in their teens and started an international touring career in their late 20's.
Could you please elaborate some more on this story? I would really love to hear it. For some context, I've been struggling with the same question as the OP and I started as a late teen. I've been able to progress quickly enough to where I'm now able to tackle the Ocean Etude, but it's always at the back of my mind if I can ever truly achieve fluency.