I'd say it depends on your goals, do you want to be fast at a club level, national level, international level?
For the higher levels of competition I am convinced sprinters are born, not made. Of course any successful sprinter needs to be willing to do the work and give every effort 100% but without the right genetics you will only get so far through training.
I think from the endurance side things are far more trainable although still to reach the top levels of the sport, genetics factor in.