Competitions mean very little. They are useful in order to grow the ego of some of the prize winners and been the battlefield of several teachers/schools/politics, but they doesn't really mean much more more than that. The true and charismatic artist will achieve success sooner or later (sometimes thanks to competitions, sometimes without them and other times despite of them. For instance, we have the strange case of the participation of Ashkenazy on the 1962 Tchaikovski Competition. Why the heck did he that? He was already a worldwide star!) Horowitz never participated on a competition, and so on... And for the other ones, they are nothing more than what the word means: prize winners, nothing else. Unfortunately most competitions in the world are a junkyard where political, relationship, connections, economical or whatever criteria is more important than the artistic one. That's just plain garbage.
I can't remember if it was Nadia Boulanger or Margeritte Long but she said that the parisien piano cafes were full of first price international competition winners.
Thank God, there are many means other than competitions to build a concert career.