A couple of thoughts on this, coming from a Bonvoy Ambassador member (so I do like my Marriott stays too). I guess the first question is, if you've never stayed there, how do you know you get "just as good service at the Marriott"? Popping in to buy a snack obviously does not expose one to the entire set of service experiences as an overnight guest. Aulani is, hands-down, one of the best-run hotels I've ever stayed at (and I've spent a total of over seven years of my life in hotels). It is Ritz-Carlton caliber, and on the better end of that scale as well. I'm not saying one can't have a perfectly acceptable stay at a Marriott or that one might choose a Marriott over Aulani if the cost/value proposition isn't there, but don't dismiss the customer service as being equivalent, because it just isn't.
In terms of a "true Hawaiian or Disney experience", I'll focus on the Hawaiian part. There are some great videos out there of Joe Rohde talking about the design process of Aulani; I challenge you to watch those and NOT come away with the sense it offers a much more genuine Hawaiian experience than any mass-market hotel or resort on the islands. In fact, that is the whole reason Aulani exists and it pervades tons of details, big and small, throughout the place. If you were paying attention, even when you popped over for a snack, you should have felt the difference. If not, and all that effort is lost on you, then I agree it's not worth paying Aulani's premium prices.