I agree with everything beetnemesis has said above, but I also think some of the blame can be laid on how Aes Sedai train their initiates.

There were, what, forty novices in the Tower when Egwene and Elayne first joined? Of which only two or three were expected to make it to the Shawl? The Tower established ridiculously high standards for itself back in the days when it could afford to pick and choose, and were too proud to lower them later when not enough women were making it to the Shawl. And of course, you have a mere two years of eligibility for enrollment - are many girls brave enough to leave home at sixteen? - and there's the fact that even talented initiates can die in one of the tests.

I don't think the Tower is bad at recruiting so much as its bad at managing those recruits. They've made the status of Aes Sedai nearly impossible to attain, and left no place for those who can't measure up. They're wasteful.