I don't know that the selection is so bad. Some of them were certainly bad, but if you chose a group from outside politics, you would also have that. I think part of it is the whole exercise puts them under a microscope and everyone judges every little thing they do or don't do, say or don't say. More importantly, they judge them on bits and pieces of sound bites taken from hours of talking on the campaign trail. I think in these conditions, a good portion of voters would refuse to vote for George Washington much less one of today's politicians.
I find it funny that I still hear people being critical of the unpolished statements and such from Trump when it is exactly the unpolished "speaking his mind" image of Trump that a lot of people like. I also laugh that sometimes the very things they don't like seem to generate the exact reactions we want from liberal Democrats.
Most of us have all said we want candidates to say what they think, but few are really prepared for the fact that most people are not well spoken or versed when they speak their mind. They will misspeak, say stupid stuff, or sound crazy at times especially with the media taking a few sound bites from 30 minute speeches. Politicians' habit of saying nothing is a learned behavior due to the way our media and our voters react to the things they say.