Yep, it's the system and Gasperini that are the real stars. Just look at him, he keeps doing this again and again after players leave or get injured. Who thought that they would finish even better than last year, especially when Zapata had a big injury right away? I do think they're outstanding footballers, don't get me wrong, I rate half their starting eleven as better than literally anyone Juventus have, but most of them need the right context to work and it's being provided by Gasperini's philosophy. It's a bit like how, for a long time, players always performed much better at Arsenal under Wenger than they ever did elsewhere.
Gosens is the main one I would sign I think, he's only 25 and has everything needed to be a top class leftback/left midfielder for another decade. We don't really need him though, we have Tierney and Saka occupying the same spaces.