I wouldn't worry about the story being as relevant as the atmosphere and effects. The Haunted Mansion just *feels* like the 1960s and that's a problem. Disney has already said that they are worried about the mansion being relevance to today's audience, hence the addition of more effects and technology.
I don't think gutting the whole thing is the answer, but I would like to see more effects and technology added. The video projectors in Nemo provide a much better experience than the peppers ghosts effects. I also think they should remove the scrims in the graveyard. If they want fog - they can bring in fog machines. The scrim projections never work right anyway.