Funnily enough, I was just thinking about the wendigo issue earlier today, and this is the second time I've seen posts about it since then.
When it comes to accusations of cultural appropriation, they're usually bogus because the original culture has not actually lost anything and so no theft has occurred. See every case where a person using some popular internet slang coined by a black person, wearing a tribal pattern, or owning a dream catcher has been accused of appropriation, when in fact they're appreciating and even helping the culture by preserving and spreading it. The wendigo, however might actually qualify, because in a sense, the name of the creature has been stolen. When you say "wendigo" people think of the popular deer version instead of a real wendigo, so the people who use the term as it was originally defined will always have to clarify themselves for the benefit of the masses, and the audience for "wendigos" will seek out modern cryptids believing they are traditional.
This is comparable to the "biblically accurate angel" which has gained popular appeal and is thought by many to actually be a truthful representation of the angels depicted in the bible, to the point that some ridicule christians for seemingly not understanding their own holy book because they use the correct depictions in which the angels look like normal men. And what originally put me on this train of thought was a post someone on here wrote the other day (I don't remember which thread it was in so I can't find it right now) about fandoms being ruined by reboots, and the argument that it doesn't matter because the original still exists. However, as the poster argued, when the new version supersedes the original so that most people only know the reboot, the media only panders to fans of the reboot, all the merch that's made depicts the reboot, people attribute the virtues of the original to the makers of the reboot, etc., then the original version's place in popular culture has indeed been lost, stolen, or even appropriated.
Somehow I don't think the people yelling about how white people are appropriating indigenous american magical practices and religion by saying w*nd*g* would be very sympathetic to the argument that the tv show The Boys is culturally appropriating the comic book it was based on.