>>12156714You (((can))) learn a skill at any age. You won't learn it at a professional level. It won't be profitable. Learning alone requires time, time which could be spent specializing the career you already have.
If you have a hobby that happens to be productive, good for you, but don't expect that to be your moneymaker, it usually isn't, and when it is, the previous thing you had dedicated your life to goes to waste.
The most useful skill someone can ever learn is how to get people to do shit for you, because you can't do shit that matters alone these days.