Jack will definitely improve and in overall - no question can be asked about this transfer, because we definitely needed to strengthen this area due to reason that Gundogan will be 32 soon and Kev also is 30, which leaves us only with the Bernardo and Foden - who was playing as a winger for whole season and today played as a false9, so you need attacking midfielders and Jack was (and is) one of the best in the league.
So this is transfer for future and therefore you shouldn't judge it in 2 or 3 or even 12 months.
And still we see glimpses of his brilliance - like that goal against Leipzig or even today - he was very unlucky not to score there, considering how Jesus scored :D