On that we agree. I prefer that hosts took the responsibility and picked the top 10 winners themselves - with comments and reasons.
For me, I want group feedback.
But people do not leave feedback in challenges, so it is not the best vehicle for that. And if you meant indirect feedback by voting, it is somewhat iffy, particularly with voting irregularities. Besides, art is not an egalitarian discipline. If art galleries were forced to be self-sufficient (charge enough to recover full costs of operation), most of them would go out of business.
Let's assume for a moment, however, that you believe all voting is perfectly honest and above board. Tell me, who do you want to learn from, those who are better than you, or those who aren't? How many who are truly excellent in your particular interest area in photography do you think vote in any particular challenge that you enter? How many of those vote on your photo? The chances are that if your photo is superb or really lousy, it will get noticed for more than a couple of seconds and will get the deserving vote. Otherwise, it will be skipped or given an offhand 1.5-2.5 "me-too" vote that doesn't really mean anything.
See, the odds that you will actually learn something by votes received if your photo is not in one of the extremes (superb or miserable) is negligible at best.