Hand flying skills and decision making ability are both mental skills.
We should have mental resources to do both simultaneously, shouldn't we?
Imagine that your hand flying skill is degraded due to lack of training and practice.
If the time comes that you have to hand fly and make a decision, your brain resources for decision making will be greatly reduced because you have to fly the damned airplane.
Or, God forbid it! you will be making a decision proccess with the D.E.C.I.D.E. or any other nice achronym while the airplane flies you. And doing all checklists and call outs until the CVR stops recording.
A skilled hand flyer has a better situational awareness than a non skilled hand flyer, all other characteristics being equal. So he is safer.
A TRE I know says that he often sees crews crashing with only an Auto Thrust inop. Sometimes with only one channel inop!
I have seen people in sims cancelling the master caution every five seconds and wondering in anger why the f*ck it keeps being triggered... (only 320 pilots can understand, maybe?). I have even seen some to reluctantly hold the thrust levers as if God himself had abandoned them.
If this is happening, then something is wrong in the system.