TRON is so short that it doesn't add that much to the park's capacity (beyond the people waiting in line for it, of course). If you have two rides that can both get through 1000 people an hour, but one is a minute long and one is 15 minutes long, the latter essentially has 15x the capacity of the first because it's keeping riders out of the park 15x as long. Of course that's overly simplistic -- it's not really 15x because you're likely spending more time in line than you are on the actual ride; it would only be 15x if everyone was able to walk-on with no wait times at all -- but it's demonstrative.
Two 5-10 minute long dark rides (which they could certainly fit inside that gigantic box) with a similar hourly capacity as TRON, even if they each had a wait time half as long as TRON's, would be functionally/operationally better for the park.