As someone who's been on the party side of trying to get candidates to run for office, it's a whole lot harder to do when
a) The people who would be a great elected official aren't rich;
b) They don't have all the time in the world to devote to campaigning;
c) They don't have much chance of winning because the local electorate are +25 r.
d) They don't have the necessary personality to survive running for office. Are you aware of the type of person who tries to get elected? Let me assure you: Anyone who does that needs staggering self-confidence not to get torn to pieces from running that gauntlet. The problem with such people, though, is that they're used to winning in life. That means they hate--nay, LOATHE--to lose. At anything.
They also tend to be smart, so they are aware of how some races would be a waste of their time because they know they can't win. It's just not worth their time and effort. And if they won't run, then it becomes well nigh impossible to find anyone else to do it who doesn't have a screw loose.
But if you think it's so easy to find candidates, build a support team around them, lock in the funding, and get them elected, then by all means, please go down to the local Democratic HQ and show us all how it's done.