The game isn't finished, period. Nintendo is launching it on May 29th because they have to. The Wii U has nothing releasing at retail and releasing this in August would be a disaster. It's completely ridiculous that the company is still incapable of releasing software in a timely manner but it is what it is. I'm still buying it, because it looks incredibly fun and at least all of the future content is free. As for reviews, journalists should review what they're given before launch. Reviewing a game based on upcoming content isn't a good idea.
Two things really bug me though:
1. Since the game is missing a lot of content at launch, it should not be $60. Nintendo would be very wise to rethink the MSRP and lower it to $50.
2. The Amiibo support is downright offensive. Three of the four arcade minigames are locked behind them. Nintendo is now using Amiibo to legitimately lock actual gameplay content behind them, not just skins and fun little extras. It's extremely troubling to me, personally.