Innoventions is definitely an apt comparison, and it's telling that the team that dreamed that up was the same team that put together DisneyQuest. Additionally, many of the attractions that wound up in DisneyQuest were actually based on technology demoed at Innoventions first, most notably the VR helmets.
Well, the thing with the MagicBands is this: I definitely enjoy them, and have found that they've improved my vacation. However, they cost the Disney company well over a billion dollars to design and implement. That's an awful lot of money that could have gone to other projects, such as revamping Epcot. As you say, an app might eventually become outdated as well, but it only costs a few thousand dollars to build an app.
To me, it's about cost and benefit, and I think the enormous cost of the MagicBands doesn't cover up for the fact that the benefit is only minor and might be deemed obsolete in the near future. The fact that Shanghai isn't even using them is a red flag that suggests WDW spent a billion dollars on a gimmick.