I don't understand why we are going on the direction of removing the possibility to fully get access to the private keys?
Having no access to export individual private keys isn't depriving users access to their private keys.
The command
listdescriptors true is always available to get his master private key anyways.
Refer to my post above regarding the reason for removal of dumpprivkey command in descriptor wallets.
For the depreciation of legacy wallets, read this article written by achow101:
achow101.com/2020/10/0.21-wallets