If you have a car, you should have enough time.
Fantasmic is 28 minutes long, so a 7 PM show will be over by 7:30.
You would almost do as well if you took a bus from the Studios to the Contemporary and then grabbed the Bay Lake resort launch. The launch, unlike buses, will drop you a few feet from Pioneer Hall.
Another idea is to bus to Wilderness Lodge and then transfer to the launch. Yes, in both these routes, you’ll need to walk from the bus to the dock, but if you do, you won’t have to deal with the FW loop buses or rented golf carts.