Crew hours
Just as a point of reference and not pointing any fingers at quals, the Capt is reported to have 8,000+ hours and attained capt on 737 type in November (source CEO on WSJ). AVH reporting FO as having 200 flight hours. The average fleet age is 5.4 years according to airfleet - on the youngish side and mostly wide-body.
Regardless, Boeing has some serious soul-searching to do no matter the ultimate cause and IMHO crew/maintenance training, experience, procedure blame will not be sufficient.