One argument would be that we don't promote youngsters because we don't have any great ones atm. The other would be that we don't have any great ones, because we don't promote them like we should anymore.
It is a combination of the two.We sure don't have many great talents atm,but i believe that guys like Montoya and especially Bartra would have been benefited by a much bigger playing time.
What about the current youngsters?Well,i believe that Bartra is a quite good talent,but the coaches and especially Lucho don't believe in him really much.I mean, i'm ok with Matthieu,but there was no reason to buy the Verminator...And now i am hearing that we want o buy another CB...As for the midfield prodigies,i hope that Rafinha may someday replace Iniesta.Roberto should stay for rotation porpuses,like a new Keyta for example(if he can accept this role).Samper should be handled with great care,as he is a potential Xavi successor.As for the attackers,they are just really mediocre...As if this wasn't enough for them,they have to dethrone one of the MSN.Only Munir may develop to a decent backup attacker.
In conclusion,just because right now we don't have neither quantity nor phenomenal quality,it doesn't mean that we should abandon Masia and become the new Galacticos...The Masia should always be our first source of young talents.So,we must put great effort in this institution.If,and only if,the Masia fails to produce talents,then we should buy talents from other teams