That's unnecessarily and destructively cynical. There are plenty of politicians (and others working for governments) at all levels who are there to do a good job.
The showboats and bad actors (which are almost coextensive) of course by definition get most of the press. Don't let them distract you.
That leads me to the conclusion that the best way to influence politics is not through the politician themselves, but through advocacy groups that can shift the political incentives.
Even the politicians celebrated by history made awful compromises to maintain a winning coalition. LBJ's relationship with MLK for example.
The statement was about how they're selected. They're selected by their eagerness to be in politics, and their ability to talk a good game.