Well in my slightly less than 14000 hrs I've had many autopilot failures from total loss to mode fails. F/D's not agreeing, or displaying total nonsense so to put all your eggs in the basket of autoflight isn't sensible either.
Pilots do make mistakes, but we do still need to keep our hand flying skills sharp. No "system" designed by a human is perfect, so we need humans to make up for odd stuff up.