This is a title I would be interested in if it didn't require amiibos to play. I'm very much an all-or-nothing person, so I've avoided buying amiibos since I don't have the money/space for them all & if I only bought a few it would bother me that I didn't have a complete collection.
I'm already put off by that aspect. To me, it's like selling a board game where you have to buy the essential pieces separately. That & the way they announced it. Seriously Nintendo, you knew how much hype there was for an AC Wii U, if you're going to make a second spinoff, don't make it seem like something it's not.
The way I look at the Wii U recently, and the direction it's going, is that soon amiibos will be required for any game the Wii U plays (that, or cards like that Happy Home spin-off).
As far as I know (I could be wrong on this), the Wii U is the only game system which uses amiibos to enhance the gameplay experience; in order to unlock certain things and characters, rather than do it in-game, an amiibo is needed for select Wii U games (such as SSB and Amiibo Festival).
I'm really not surprised that it requires amiibos to play; Nintendo got a lot of money off of SSB for the Wii U and all the amiibos they made for that. They certainly wouldn't stop doing something which works (especially if it's getting them more money).
Since the Wii U wasn't (and most likely still isn't) as popular as the 3ds, Nintendo had to do something to save the dying platform (and there was one point in time when everyone was sure that the Wii U was going to die out completely); so, Nintendo introduced amiibos.
Am I surprised that all fans got were these spin-off games considering what sort of console the Wii U is?
No.
However, I'm sure that, when the game is released, parents will be buying it for their kids..and diehard fans of the franchise will at least buy the amiibos (as some people in this thread even said they would).
As for the debate over it being "free to play"...even if it can be downloaded for free, it's not really "free to play" if you need to buy amiibos to actually play it. Like LaBelleFleur said, it's like they're giving the game without the pieces; so in that thought, it's not really free at all since the software is useless/unplayable without the amiibos.