It's all about perspective. For instance, being a lifelong series fan I got all the Zelda amiibo before we even knew BotW would use them in any way, just because I like having the figurines. The fact that they're good quality for their retail price also helps. The way I see it, I got a few cosmetic items extra. In all honesty, they were pretty useless in the game, so no one is really missing out.
Amiibo aren't the same as on-disc DLC. The latter is when a game is close to completion and then the dev/pub decides to lock content for some more cash flow. I don't think any of those items would have been included in the game if it wasn't for the figurines. After all, no other Zelda game has had the tunics from past games.
Wolf Link is the only functionality that's impossible to get otherwise. But even after leveling him up near max in TP HD, he still dies in no time and takes forever to eat the food you give him to replenish his hearts. The only thing useful about him is that he gives a different feel to the game when exploring. I wish they'd had made that into a mechanic that allows you to turn into a wolf when your hearts run out, or something along those lines.
The only issue with amiibo is the fact that Nintendo keeps arbitrarily making some of them retailer exclusive, which is both a pain in the ass and hurts your wallet even more if you're planning on getting each online. There is no excuse for making each of the 3 anniversary Links exclusive to one retailer. They definitely know lots of people want them all and yet they keep doing this.
Can't talk about other games since BotW is the only game where I used amiibo on but that's my 2 cents on the matter.