Curation should be an incentive to find and upvote quality content but as it is people try to maximize it by following and uptvoting authors (not content) that they expect to get more rewards. Besides that, the best efficiency on upvoting power is only achieved by bots (or an extremly disciplined human) and this also benefits bot curation which hardly ever is content driven.

For it's purpose, curation fails to achieve what is necessary for steemit to grow, that is making people see it as a usefull and fair plataform, where you can find good content easly and get rewarded by helping others to do so.