Here you're wrong. The CIA and some other members of the IC are very selective in who they hire, but not in the way most top-tier companies are. The issue is applicant clearance. So if you're a genius, native-US born linguist who has lived in several Middle Easter countries, speaks Arabic, and has a honors degree from a top school, or a brilliant mathmetician/computer scientist who studied in Eastern Europe and married an Eastern European, it's relatively hard to get the level of clearance you need for the CIA, because of the way that foreign residence and/or family and friends count on your clearance questionnaire. And if you've got this background and smoked a couple of dozen joints in college, getting a clearance becomes near impossible.
On the other hand, if you're a community-college educated applicant with solid grades and military or law enforcement experience, and no foreign residencies or drug experiences and/or alcohol-related misdemeanors, you're golden. You allude to this phenomenon.
But while it relatively easy for a certain kind of applicant to get into the CIA, it's far from the truth to say that they're not selective. They're incredibly selective, and they're excluding some of the most promising candidates that apply because of their particular kind of selectivity.
Beside the loss of many highly-qualified applicants (what serious language expert hasn't lived overseas?), this is also said to create a certain culture that bears more resemblance to boot camp than to the highly-professional organization the CIA has been traditionally. Snowden alluded to this in his interview.
This is not a secret problem. In fact, there were quite a few public Senate hearings on the issue after 911. But nothing much is reported to have changed.