If you look at the teams of the 80s and 90s, it was Real Madrid who was more successful at producing a homegrown core. I mean really, is what Barca has done any different than the Quinta del Buitre?
Obviously they did. Miguel Pardeza, one of 5 members of Quinta del Buitre, played only 28 games for Madrid and moved to Zaragoza, so there was 4 top cantera players really not 5. In Barcelona you have: Valdes, Puyol, Xavi, Iniesta, Fabregas, Pique, Messi, Busquets, Pedro, Thiago, Fontas. That's 11 not 5 and 10 of those 11 played more than 28 games and will play many, many more. And they are crucial part of best Spanish NT in history. There are many talented players in La Masia nowadays, not all of them will make it obviously but some will very soon. What FC Barcelona is experiencing nowadays has never been matched with such an enormous success, both at the club and NT, it's something very extraordinary.
It won't be the same all the time. But no-one expects new football legend (xavi, puyol, messi) from the academy year by year. A crack every few years, and reliable source of squad A players will do fine. And it's working as you can see how midfield generation changes (Xavi 32, Iniesta 27, Fabs 24, Thiago 20). The youth coaching methods mutated bye time and improved steadily benefiting from experience, and the same happened with scouting. It's that big collective work and gained experience from several decades what Barcelona is benefiting from lately. And will in the future.