If you think about what they were doing and the fact that most of the "old men" of the squadrons were in their early twenties. How many twenty year olds would you trust today with the keys to the Liberator?
My Grandpa mentioned that the "qualified" pilots mostly came right off the farm. They had more experience with heavy machinery, which made them more qualified to pilot than the others. He told me that the crews learned most of their skills on the flight to Europe. His crew went south into South America, then crossed over to Africa, then back up.
Yea, I am not sure how many 20 year old kids would qualify today.