Sergio Busquets was the only Barca player to start in either of the UEFA Nations League games for Spain.
"It's surprising there's so few Barca players in the national team, but there are cycles," said Del Bosque.
"It doesn't speak badly of La Masia, there are eras, but no club should forget about youth football."
He added: "Busquets' leadership is the best possible. Without Sergio the success of the national team would have been a lot harder."