The thing about playing music as a kid is that, yes, you pick up things more quickly as you develop as a person (the same way you do with language). But here's the other thing: I know a lot of people who were talented kids who went NOWHERE, because they never developed their talents or couldn't get past a stage of immaturity to really get their playing off the ground. 24 year old musicians are generally much smarter than 13 year old musicians. They can more easily understand what they need to work on and oftentimes level out their own ego.
I'm 23. I started trombone officially when I was about 14 but didn't really start getting serious about it until I was in late high school (I hadn't really taken private lessons until then or even really practiced very seriously). I went to a decent jazz school, practiced a ton, then transferred to a very good jazz school. Now, I'm not anything to drop a jaw over, and there are many other trombonists here in the city who would rip me apart in a jam session and are called for gigs way before I am, but I'm pretty good for NYC-level kids my age. I can be hired for a number of styles. This is because I'm constantly trying to work my everlasting butt off to keep up. I can envision myself at this stage in the game eventually being one of the "on-call" cats in the city, if I keep my head straight (of course, that relies on how many gigs actually EXIST, but that's a whole other story).
What I'm saying is that dedication, practicing SMART rather than necessarily HARD and being conscious of your own development, it's not "too late". Like anything, it gets harder when you get older, but you're not brain-dead at 24. Joe Pass, one of the best jazz guitarists ever, honed his skills and emerged during his 30's.