I think it comes down to the lack of competition when comparing it to other WDW coasters.
With Primeval Whirl gone, there's now less than 10 of them across the whole resort, including the yet to open TRON.
GotG is
at least among the best WDW roller coasters right now...because the competition includes Barnstormer, Slinky Dog, RNRC and the badly aged Space Mountain [which should be a lot better, but that's another issue].
I'd say BTMRR and Everest are both better for not being giant boxes, but it's not hard to understand why someone would think GotG is more fun at its core. It's at least not as disappointingly short as Seven Dwarfs.
As
@bhg469 said, if you don't do much outside of WDW when it comes to theme parks, you'd probably be impressed. The lack of major new, built from scratch EPCOT rides over the last 15 years also makes its arrival more exciting.