It is and it isn't. There are professional athletes who start doing their sport at 7. If you start at 29, you'll quite probably never make it to the top. At the same time, you could surely make it to the top of an orthogonal career, such as one of the top coaches.
On the other hand, things that mostly stretch your mind, such as science disciplines, you can do well in your 70s, 80s, or possibly even 90s. If you start at 29 with studying physics, you could get on top of your field by 45-50, leaving you quite some time to enjoy your top of the field.
29 is fine to start with most things I'd guess, especially if you've got experiences you can bring to your new career that others might not have.
On the other hand, things that mostly stretch your mind, such as science disciplines, you can do well in your 70s, 80s, or possibly even 90s. If you start at 29 with studying physics, you could get on top of your field by 45-50, leaving you quite some time to enjoy your top of the field.
29 is fine to start with most things I'd guess, especially if you've got experiences you can bring to your new career that others might not have.