Ake is average and City will find that out. Chelsea fans only rue De Bruyne and Salah as they were bought cheap 7m and 11m respectively then sold by Mourinho and was terrible business by a manager that does not develop players.
Van Aanholt is rubbish.
Tomori is a better centre half than either Ake or Van Aanholt and other home grown players such as James, Mount, Gilmour, Abraham, Hudson Odoi, Christiansen and Loftus Cheek have all many games under their belts and secured 4th place with their ages between 18 - 24, plus another 6 or 7 pushing the first team - the future looks quite bright.