Young pilots on large aircraft is nothing new, and as fas I'm aware there is not much of a correlation between the two regarding accidents. This goes from the days of the war (dambusters etc.) up until the days of hamble and teenagers flying large jets for BA as well as numerous other European carriers.
It is nothing new and it's unlikely anything will change soon. In my experience most of those who complain about it are those who for whatever reason were never able to get on a course and in many cases it's simply an instance sour grapes.
One thing I can certainly say is I've never heard anyone with extensive flight training knowledge or industry background knock or speak ill of going from flight school straight onto a jet.