Extortion: obtain something by force, threat, or unfair means. At best you could call this 'unfair,' certainly not threat or force. I think the statement that it is unfair needs to be called into question, as believing all of this content should be free to the consumer is what is actually unfair, and ridiculously greedy.
I think wanting a ton of free content, for Nintendo to offer lots of free service, and to then want to pay nothing towards it, is actually you trying to extort them.
Smash Bros by itself is worth more than double the price of the actual game, considering how much replay value it has. I do not know many many people simply play it once or twice, it is played far more than most titles. If you take that into account, it is worth far more per dollar than most games the average (that is mean, median, mode, or range definition of the word average) consumer buys.
No one is forcing you to buy an amiibo, just as you do not need to buy every piece of DLC in any other game. In fact, in this game it seems you truly do not need them even to unlock everything (so far, compared to other games which have DLC for tons of micro purchases). Even if it were that way, I would not at all blame Nintendo, as this is their most profitable franchise, and could easily be their way into continued success in the future, ensuring future installments of this franchise can even exist.