Even in the last years, I remember Barcelona had good midfielders but they didn't have very good forwards and their team was not dependent on the forwards they have, they usually score goals by using the midfielders they had.
This season Lewandoski was a good performance but I think if Barcelona wants to hire new players they definitely need to hire a young forward to take his place for the next season.
I remember last season Barcelona really struggled to score goals before Xavi came. But after Barcelona signed Xavi then some players like Dembele and Aubameyang really made a good impact in attack. Barcelona's number of goals increased and they became more confident about winning the title even though in the end they had to be quite satisfied with ending in second place. Xavi tried to sign Lewandowski, it turned out to be a great signing for Barcelona and he proved that with a top scorer in his first season.
This season Ferran and Ansu Fati haven't had much to contribute to Xavi's attack, but both have become important players when others have been out injured. Dembele, Lewandowski and Raphinha are Xavi's main players in attack, so their lack of competitiveness is the reason why Ferran and Fati are often on the bench.