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Mind you, Barcelona had Messi from when he was small, hence the reason why the team seemed to have been built around him. It is way easier to train a star player from small. He is more like family until he has gotten to the peak with them when he may not be able to perform as much, that's why he was let off too.
Right now, any start player they have will have to have been groomed from the youth team, do as to fit well within the managers plan for the season.
There's nothing wrong with your assumption, and so far Barcelona has still adopted the same way where they always have a few players from their own academy. They are poised to be the star players of the future, it is the next generation of Barcelona that will lead the team to glory. It's just that Barcelona's financial condition is very likely to make some players to leave especially if they expect a higher salary.
Gavi, Pedri, Ansu Fati, Balde, Araujo and several other players are the academy players I mean. So they really understand the condition of the team and they also seem willing to help the team to get their glory together again. The great thing about Barcelona's current players is that they are willing to lower their wages and continue to want to stay in the team for the long term.