I think you have to have a good mix of all types of rides. WDW has to look at what will draw all people in.
The thrill rides catch peoples attention, Snow Whites Scary Adventures doesnt, for example. Thats not to say that once people are in the park that the ride doesnt draw people, its not enough though to get people to make WDW a vacation destination.
Busch Gardens Williamsburg or even Carowinds in Charlotte is a lot closer for us to drive to than WDW. And they are loaded with thrill rides. BG is especially nice to visit. It is clean and the atmosphere is much like WDW. Not as enjoyable as WDW, though. So comparitively speaking, both of the other parks have more thrill rides than WDW, yet we drive an extra 6 hrs to get to WDW vs the others. Why? Not because of the thrill rides but because WDW is what it is. There is a magnet that draws us to it each year, if that makes sense.
I too like those dark rides. That makes WDW special, the mix of rides and attraction that they have.
Bottom line, IMO, is that WDW has to continue to build rides and attractions that draw lots of newcomers and past guests alike. If not, us oldtimers wont have a WDW to go to if they cant draw the crowds.