What Guardiola said, and it does sound uncharacteristically dismissive of him, was that Wilshere is an excellent player who is lucky he plays for Arsenal because the pressure to win titles there is not as high as it is in Barcelona.
If he's correct that the Barça B is rife with Wilshere types, then that club has bigger problems than I thought. To get to the first team at Barça you must be a finished player, and to get there at 19 or earlier, like Messi, you have to be extraordinary even in this context. This is the reason why the Fábregas and Jon Torals of La Masia end up at the Arsenal. They are quality and they know it, and they want to play. They don't want to end up like Iván de la Peña, who was once justifiably rated as highly as Raúl González.
Guardiola, to his credit, has brought up many players from the system, something neither Rijkaard nor (notoriously) Van Gaal were wont to do. But if the path to first team ball is blocked to great players, those great players will find their way out.