^Experienced both for the first time last spring. FJ fell below my lofty expectations for a number of reasons while Gringotts met or exceeded them. I'd go as far to name Gringotts the best attraction in Orlando since Tower of Terror.
For me, the biggest test was the set-to-screen integration/transition. FJ's is somewhat jarring and took me out of the moment, whereas Gringotts was much better integrated in both the queue and ride.
FJ was groundbreaking. Gringotts is not.
But Gringotts is also a ride that more people can ride. FJ is borderline extreme. I know I had some concern putting my 70ish parents on it a few years back.
I don't share your, or the UNI Wand Wavers, enthusiasm for it at all. It is fun and quality, but not special at all.