Kim is 25 and Timber is only 21, so Timber still has time to learn. Timber himself felt he wasn't ready for United and that is why he stayed at Ajax and we signed Martinez (24) instead. Those three and Ndicka (23) puts us in very good shape for the next 5+ years as Varane's (29) career winds down.
I agree with letting go of Maguire, Lindelof, Tuanzebe, Jones and Bailly, and three replacements doesn't sound excessive, especially when Timber can cover Dalot and Frimpong (?) at right back as well. Hopefully we can get enough funds from the leavers, and AWB, to cover most of the purchase price.