Some of the many things wrong with that article:
* Cultural appropriation isn't the same thing as racism
* Racism doesn't make any sense as something unintentional.
* It's not categorically, morally wrong to do something that might result in someone getting upset.
* Cultures do not "own" customs, traditions, mores, etc.
* Cultures are not isolated units that remain intact as isolated units; cultures obtain via interaction of individuals and necessarily evolve as individuals and interaction changes. People who think they're from different cultures, who are interacting, by doing so, are necessarily evolving their cultures into a different one based on those interactions. That's how culture works.
* So as people interact, they create a different culture, and that culture is their own.
* "Power dynamic" talk is typically a mess. Among the many problems with it is that it tends to cherry-pick particular facts, interactions, etc. to fit the narrative the author wants to create. If we're going to make claims about dominance, oppression, etc., then we need to set out what those terms are going to refer to in a manner that can't be seen as cherry-picked from the totality of data available, and then we need to show the empirical data to support claims about it.
* Saying that wearing clothing, say, is "taking" something from another culture employs the same nonsensical rhetoric that has been used in intellectual property discussions. That rhetoric is ad hoc, created by companies, under a capitalist system, who'd rather be able to legally threaten than have to be creative and figure out other ways to make money (where unfortunately that's necessary because of the capitalist system they're operating within).
* "But marginalized groups don’t have the power to decide if they’d prefer to stick with their customs or try on the dominant culture’s traditions just for fun." --Ridiculous as stated. There have been instances where some culture has been forced to not do certain things (clothing, language, etc.), but that has nothing to do with cultural appropriation. And it being morally wrong to force or pressure people to not do what they want to do re things like clothing and language certainly doesn't justify pressuring people to not do what they want to do re things like clothing and language, which is what "cultural appropriation" shaming is about.
* "it’s clear that not every person who speaks English does so by choice."--Obviously. I didn't speak English by choice. I speak English because I was raised in an environment where only English was spoken. That's how language works. You only speak languages by choice when you take up other languages later.
* "It’s a complicated issue that includes our histories, our current state of affairs, and our future" -- to whom? An issue only includes those things if an individual thinks about it that way.
* "as we act to eliminate oppression," -- If one sees "cultural appropriation" as oppression in any way, shape or form, one has much more serious issues to deal with than eliminating oppression.
. . . I didn't even get to the numbered points yet, but I'll leave it at that for now, since the above is already pretty long and I'm probably more or less wasting my time posting it here.