If you don’t participate in either game, MK is the better attraction. The AR game distracts and detracts from Mario Kart’s sets significantly.
I mean, on paper we shouldn’t be comparing them. In practicality though this isn’t a one off opinion.
Had this tech been used instead for Luigi’s Mansion and the ghosts interacted with the physical props, it would be a significantly more sensible use of the tech. Mario Kart instead feels like the second iteration of an attraction where they’ve overlaid something on top of a much more built out progenitor. The Space Fantasy effect.
I mostly don't disagree! I've had the exact same Luigi's Mansion thought as well.
But even accounting for the missed potential, Mario Kart is a vastly better ride than Webslingers in just about every metric: It has detailed sets, (rather than JUST staring at screens), actual animatronics, multiple characters, some great effects (the warping walkways), and love it or hate it, but the AR is actually unique and (mostly) works well. As you suggested, you don't have to interact with it to appreciate it; whereas Spiderman has absolutely nothing else going on.