This is also taking the argument a bit too far. Ruth today would have access to training (in season and off-season), diet and equipment that he didn't have back then. The difference in park dimensions, how tight the ball is wound and bat size would be huge for him. If he had any sort of discipline, he could still be a very good player.
He had freak hand/eye coordination, that's always an advantage no matter the era. I don't believe anyone thinks he'd be as good as he was when he was playing but I do believe he'd still be very good. To say he "would not be able to hang in today's game" is a bit much, IMO.