You're misunderstanding me.
You are positing a short-term trade-off of playing younger players that isn't really there. Give the kids a chance and the ones that can help us will reveal themselves and make us better right now.
Mason Mount was better than the guys he got games over at Chelsea. We'd have gotten much more out of Oliver Skipp this season than Moussa Sissoko.
Why not both though?
Why not bring in the youth like Skipp that are better than their counterparts and bring in some youth that might not be immediate upgrades but aren't really much of a drop off either?
In my example of Aurier and Lavinier. Neither are good enough to start in the PL so if we are getting in a new RB why keep Aurier as the back-up when putting Lavinier in there gives us hope for the future, develops a player and helps us move out guys that should be gone?
I am not saying boot Kane for Scarlett, I am talking about moving out guys that clearly are not good enough and giving youth a chance to step up. Stop worrying about whether we have replacement for crap like Aurier, Winks, Sissoko, Dier, Sanchez, Lamela, Moura and get them out even if it means short term drop off by playing a young guy that doesn't have the same level of PL experience.