I guess the problem is that for every Kim Min-Jae, Kvara and more 'locally' Eze, Olise etc, there are 10 Janssens, N'Koudous, Jack Clarkes, Ryan Sessegnons etc (I may not have chosen the best examples but you see my point) - who you then struggle to move on, and end up letting them leave for nothing or next to nothing. Of course both we and other big clubs do exactly that - but you can only buy so many of them, you can just buy all of the 'barely discovered talent'. Sometimes you strike gold, sometimes you don't. And it's all very well saying 'scouts should identify the best ones' etc, but it's not as easy as that, not for anyone. Even players like Salah and De Bruyne were thought not to be good enough at points quite well into their careers before truly 'clicking'...
So whilst it's easy retrospectively to say things like 'we should have got Kim M-J before he really hit the big big time', we only know how good he is now, it was never guaranteed that it was going to happen back then.
(Not criticising you by the way, you've not said that above at all - but a lot of people do seem to think that way, focus on 'the ones that got away who we should have signed' without realising you need to buy 10 or more prospective talents to get one of those very successful ones...)