Kinect wasn't for us. The limitations in interface between user and game are much less apparent or an issue from the perspective of the audience they were going after, which the OP rightly highlights Nintendo had created. It's predictable that Microsoft's decision to go after that market is portrayed as cynical and facilitated by a big marketing push aimed at that audience - it's almost as if they're a big, successful business behaving in a way big, successful businesses do when targeting a new segment. MS and Sony rightly went after a big old slice of pie Nintendo had created, not only for the new customers it brought to the party but to stop existing customers adding another machine to their ecosystem to placate new casual gamers in the family. It was as much a defensive move as it was a cash grab.
As for the Kinect itself, as has been pointed out it was crap for more conventional gaming experiences, but really very good for the kind of fitness and dance games those casual gamers were attracted to - that's the point! Put it this way, my wife has bought two pieces of gaming hardware in her life, a Nintendo DS, and a Kinect. Games like Just Dance etc were right up her street, and once she'd got bored of that and fucked off for a shower, I could put a proper game in and the console continued to get used. The Wii I bought for us gathered dust and eventually got sold on Ebay.
The Kinect was a failure, but dressing it up as a catastrophic, cynical brand killing piece of corporate dogma is a bit dramatic. They took a shot and hit the rim, and they learned a fair bit in a technological sense whilst at it.