Some more thoughts.
Okay, so Nintendo really, really pushed for AR. Fine. What I can't understand is how, at some point in the development of this thing, nobody took a serious look at it and said, "we've got something here, but it's not Mario Kart.", and reworked it into a concept that wouldn't automatically be a letdown. Though even with re-skinning the ride into something Not Mario Kart, it's not good enough to be the land's E-ticket. It's like Galaxy's Edge with only Smuggler's Run.
Second, I agree with
@Fox&Hound above. On top of it not being anything like what riders will anticipate, the AR visuals are a cluttered mess. Again, maybe it looks better in person, but the consensus seems to be that it looks "better" but not great. There is too much chaos happening, too much to focus on, and it isn't exactly clear what is happening. The graphics fill your field of vision most of the time. Even the shells you shoot/spam fill your field of vision. It looks very much like a prototype of a better final product, if you ask me. It's also one of Universal's continual shortcomings in ride design - overwhelm the riders with so much chaos that they'll be unable to process all of it, and hopefully walk off under the assumption that it was "good", despite not resonating with them at all. Better ride designs use clever visuals to guide the rider's attention to what's important when a lot is happening.
Now, regarding our
Need for Speed and demand for something akin to Test Track/RSR. It's true that RSR also wouldn't accurately convey a Mario Kart race, because the race would be 30 seconds long. However, my thought is that it definitely didn't need to be Test Track's 65 mph or RSR's 40 mph. Even a handful of, say, 15mph segments would have done wonders. That speed, combined with narrow tracks, plus smaller ride vehicles, plus built-in spinning or "drifting" would have done wonders toward feeling like a proper Mario Kart ride and being a family thrill ride. I envision these faster segments divided up by slower show scene segments.
Alternate option - although yes I would prefer to avoid another ride of this style at UOR, the Spider-Man ride system is so perfect for conveying Mario Kart. Screens utilized for the fast parts, physical props and sets for slower parts. For instance, say, during a fast-paced screen segment, a blue shell hits you and knocks you off course. The ride vehicle moves to the next zone - a physical set where piranha plants are attacking you. You escape and use a mushroom to blast back onto the course, and into the next screen/race segment.
I feel that both of these concepts convey Mario Kart much better, and neither necessitate interactivity.
If the plans for Epic Universe eventually still proceed forward, I hope they reconsider. There's enough time now.