Internal competition for places is what helps drive standards, just look at Sterling's comments about City bringing in new wingers and how it pushed him on even further. The same has happened with Walker, Cancelo comes in and Walker's upped his game again. We're doing the same I think with Zack Steffen to push Ederson. Jesus coming in made Aguero step up and change his game to Pep's demands.Age isn't a big concern to me.
After 5 years, it means some of the youth CBs have a chance to break through, earliest of them all is Tosin.
The academy has 4 great CBs from what I've read: THB, CJ, Luke, and Finley.
I'm the single biggest advocate for giving academy players a chance, however they have to earn the right and force their way into the team (e.g. Foden). You don't create a space for them by buying a stop gap signing, that's just weird logic.