Youngsters dont progress by playing when already up 4 or 5-0 and nobody in the team care to put in much effort. Thats not how Rijkaard and Pep developed players. They were given responsibility and playing time in minutes that mattered.
What domestic players have Rijkaard exactly developed?
99% of matches in his 2nd and 3rd (his best Seasons) he played with:
Ronaldinho - Eto'o (Larsson) - Guily (Messi)
Edmilson (Marquez/Motta)-Xavi (Van Bommel) -Deco (Iniesta)
Van Bronckhorst (Sylvinho)-Puyol-Marquez (Oleguer) - Belletti (Oleguer)
Valdes
Basically, Rijkaard only gave a chance to Messi, but he was the best young player in the world and the next big thing even then.
He developed Oleguer, but he was later sold to Ajax, because he wasn't good enough for Barca.
Also, he tried with Damia at Rb, but he ended as Sergi Roberto/Montoya.
Rijkaard didn't play any youngsters when we were winning/fighting for La Liga and when we were winning Champions league.
I checked now, youngsters in our team in 2004-2005 Season were:
-- Fernando Navarro, Joan Verdu, Damia, Rodri, Javito
-- 5 awesome La Masia prospects
-- none of them turned into a player good enough for Barca
-- not only because they haven't played, but because it turned out that they aren't good enough
In 2005-06:
-- Rodri, Pitu, Carlos Pena, Joan Verdu, Jordi Gomez, Cristian, Martos, Ludovic Sylvestre, Paco Montanes, Jesus Olmo, Andrea Orlandi, Ramon Maso
-- again, none of them turned into a playable Barca material
-- most of them today play in a weaker teams or in lower divisions around the world
-- they were all very good La Masia prospects
-- the same can easily happen with Montoya, Bartra, Adama, Delo and co
Again, except Messi. But again, it was extreme hype around Messi even from the earliest age and he was playing awesome in each 10-20 Minutes which he was given from the day 1 (again, unlike Montoya, Bartra or Roberto).
Pep played more youngsters, but again, we were "luckier" with youngsters in his era. Plus, as Sumlit explained, Pep had more chances to play them (not playing tight La Liga ending like Tata this year)
But when you take a larger sample, like 10 years, there we probably had around 100 prospects, and only a few of them turned into a Barca material.
So, it is extremely brave to expect that too many out of current "gems" will turn into something and that we should rely too much on them instead of buying already proven players (if we have the money, and we have some)