I think the point is not "big buys". Rather, it's about "getting" a player when required. If you think it's easy to build a team by using academy kids like Greenwood to solve the right winger problem at United, then there is a big problem.
Kindly refer the Sacho problem at City. Refer the Hudson Odoi problem at Chelsea. And finally think about Angel Gomez, Tahith Chong, Axel Tuanzebe, Pereira and that kid Ole thought would solve the Luke Show problem, I forgot his name.