I personally have a pretty high bar when it comes to what qualifies as cultural appropriation.
For me, it comes down to that word, appropriation. To appropriate something is to take something as one’s own, depriving the other party of its use. Borrowing something isn’t enough. Likewise, using something in such a way that the other party is largely unaffected also does not qualify. There also has to be a power imbalance; a weak party simply doesn’t have the capability to appropriate something from a stronger competitor. Also, there should be an aspect of inauthenticity involved, especially in representation/participation, though this isn’t necessarily an absolute requirement.
But the bottom line, though, in my view, is this: An act meets the standard of cultural appropriation if, as a result of the act, the original culture is obscured or compromised or replaced by the version being promoted or portrayed by the appropriating party. If the people of the original culture are able to carry on without their practices being marginalized or mutated by the influence of a stronger outside portrayal, if they are still able to represent their original culture fully and freely alongside the inauthentic alternative, then, for me, I would hesitate before using the appropriation label.
For example: Star Trek Voyager prominently featured a Native American character, Chakotay. The producers hired a cultural consultant to assist in making the character’s depiction as authentic as possible. As it turns out, the consultant was a total fraud, and the cultural details represented on the show were a mishmash of nonsense, half-remembered fragments stolen from various sources mixed with total fabrications straight out of the guy’s imagination. I would consider this cultural appropriation, not just by the guy but, more importantly, by the show itself. Despite having no experience with the culture in question, they wanted to put a superficial representation of it front and center for their own purposes. And by not doing the slightest bit of homework, especially into the background of their so-called expert, they wound up broadcasting a portrayal that left a wide audience with a false impression of Native American beliefs and practices, which activists have been trying to debunk ever since.
By contrast: The doofus who shows up at a Halloween party sporting a racist caricature of a Mexican bandit, with sombrero and serape and a big black stick-on mustache? He’s an asshole, but he’s not personally engaging in cultural appropriation, because nobody is going to confuse his offensive costume with the real thing.
TLDR: cultural appropriation is a real thing, but in my opinion there has to be some tangible impact — an obfuscation of the original, or confusion by outsiders between authentic or inauthentic, or a bleeding of inaccurate behaviors/practices back into the original — to qualify.