Killer passes are no use if your finishing is wank
It looks to me like his finishing is more about pressure than skill.
He scored 11 times last season, so can't be that bad, but the pressure of playing for a smaller club, when it's your breakthrough season, is nothing compared to playing for City. It's common enough for young players to go through the stages of scoring freely, then missing under pressure, then maturing and learning how to score under pressure, and that's without the added stress of such a huge move.
The joke when he started was that he was the new Mahrez, but Mahrez's first year scoring more than 10 goals was when the season he turned 25.
There are prodigies who score from late teens to early 20s, and continue throughout their career, but most players at that age are still a long way from the finished article. The problem is whether City can afford to rely on him at this age, and take the chance that he's going to turn into a great player.