So in the end, one is stuck with mediocre candidates who aren't very good. What gives?
People who are too extreme will never get majorities, hence the people who get elected tend to be middle of the road-ish, or as you put it, mediocre. (I know the word means something different, but it's cause and effect, interchange the two words in this context as you please, you get the same outcome).
It would help if you suckers didn't have a two party system. Managing coalitions in a 4 or 5 party system leads to much more interesting politics.