You are right. I think the most efficient way to raise your own level is to spar with players of a higher level. Many players will fall to the wayside because they basically cannot compete. But some players (Kendrick Lee is the best example) will play much better (than they would have) because of quality sparring partners. However, I pity players like Ronald Susilo who have no quality players to spar with day in day out. Despite that, he does well in international tournaments.