For the record, I have little to no issue with DLC, even on-disc DLC. However, I think your approach is completely overlooking all the bad that comes with amiibo versus normal DLC. As someone who buys DLC, amiibo come off as a bad deal, worse than what DLC is usually is.
I think there could be a bit of hypocrisy at play. Here's a thought experiment: let's say instead of "they do DLC right" Nintendo, imagine if "worse than Satan" Capcom was the subject here. To get the point across, let's forget about amiibos and instead focus on an equivalent that's appropriate for a software company: Physical DLC codes, like the ones you get for pre-ordering stuff.
So, Capcom says "guys, we are now printing these DLC codes, of four types. They won't be available online, you have to physically buy them. If you input one of these codes in Monster Hunter 4, you get access to a unique new weapon type. This is the only way to get that weapon type. These codes will cost 12 dollars each. We will only be printing a couple dozen thousand for two of these, available everywhere. The other two will be available exclusively at Gamestop or Target and we will be making even fewer of those. We realize 12 dollars is a lot, so this code will also unlock costumes in Street Fighter V and Resident Evil: Revelations 2 (again, only way to get this, so it'll be 12 dollars if you just want one costume in one of these games) - but only for two of them, because the Ryu and Megaman theme fits in better, while the Felicia and Viewtiful Joe ones are kind of niche and weird. Btw, all the stuff they unlock will already be on the disc, a la Street Fighter x Tekken. Good luck finding these codes before we cease printing them, you better pre-order, as there is a guy who really hates Viewitful Joe and is buying them up so no one can have them."
Compared to DLC practices in most games... how does that not sound worse? Saying it bluntly, it sounds like fucking nightmare. (The upside is that, because it is "on-disc", it will be preserved better for when people are just emulating these games ten or so years from now)