We don't need him.
Already got Silva, KDB, Sané, Sterling, Gundogan, Yaya and Jesus.
Better to save as much cash as possible to get the very best full backs, centre back, keeper and midfield destroyer available.
Using your logic, we don't need all that, we have Ota, Stones, Kolarov, Kompany, Adarabioyo, Dihno, Delph, Nando. See? It is easy to rattle off names.
We have KDB and Silva. Their lack of competition is why we keep playing KDB when he is off form right now. If we had Isco we'd have simply gone with the him and iced KDB as a starter for a while.
My vision of our core 20 squad would look like this.
Fwd: Jesus, "Mbappe", Sterling and Sane
Mids: Silva, Kev, Ilkay, Garcia, "Isco", Dihno
Def: "Semedo", Maffeo, Stones, Ota, Kolarov, "Bernat," Zichenko.
GK: "Ederson,' Bravo, Gunn
Ederson, Semedo, Bernat, Isco, Mbappe.
That will be my 5.