IMO, the basic fundamental skills of the game - kicking, handballing & marking - are something that you need to correctly develop at a young age. If a footballer has any major flaws in his kicking technique by the time he reaches 18 then it's very difficult to correct. Goalkicking, ironically is probably the exception in some cases as you can improve technically with practice given it's a straight line non-physical pressure action and kick. Field-kicking, on the other hand, is too hard to correct. Under pressure you need to be able to rely on natural instinct and feel and this is where those footballers with a poor technique are exposed.