I actually agree with this! (Look at us, coming together in agreement!) While I know Disney likes to avoid rides that don’t appeal to the entire family, I think WDI could really make something special if they tried something more “intense.”
The problem is that without heavy modification, a coaster doesn’t lend itself very well to theming. The track itself is probably the biggest challenge. How do you hide the track? Disney typically just hides it in a dark building. And if you don’t hide it, you’ve got to theme it as something other than a roller coaster track. Disney’s already done themes that actually use tracks: mine cars, race cars, runaway trains, bobsleds, etc. But those aren’t going to get you something “extreme” with rolls and loops and such. So that leaves heavy modification of the ride system just to hide it enough to tell as story and make it unique.
Plus, the gigacoasters are too tall (can you imagine Disney trying to build a warehouse to house The Intimidator 305?)!