And I replied a hundred times with a simple explanation:
the Force CANNOT guess how a 43 year old Anakin would have looked without burns and wounds.
And yes, Anakin redeemed himself, but by that time he was a corrupted man who got back on the good path before dying. So his spirit shows the look he actually had when he was a pure Jedi.
And c'mon... do you seriously Luke wouldn't feel his father? Even with a younger look?