Why would anybody complain bitterly about the system then reelect the incumbent?

Maybe if the incumbent was an effective reformer you could explain why. But we seem to reelect incumbents just because we know their names. Or because they do us or someone we know favors. Or a political organization, newspaper, or the candidate themselves say so.

The only resaon to reelect and incumbent is because we like the results they've achieved. If they can't get it done, give someone else a try.