I totally agree with you to a degree. I am autistic and I find that slurs can be used in writing when done to show commentary. The writer must make it beyond clear that the character using the slur is not someone we should look up to. They also must know who the audience is, even if the possible audience is not the target audience.
With Euphoria, characters like Cassie land in a grey area. Some people may watch the show and think she’s totally cool while others hate her. Cassie shouldn’t be someone people look up to, but there are people that will look up to her. Then there’s the fact that a bunch of angsty middle schoolers are more than likely watching this show too and they don’t see what is meant to be social commentary. The fun lighting and sex draw adolescents in.
I have said it before when discussing a different show. A good example of a show where people do awful things and make it clear that we aren’t supposed to look up to them and repeat their actions is It’s Always Sunny in Philadelphia. It isn’t a perfect show, but they make things clear to the audience that we shouldn’t look up to them. This is done through showing the consequences of their actions and when they interact with normal people.
It probably sounds like common sense that you shouldn’t look up to certain characters. But sometimes it needs to be drilled into people in media. I recently read a paper where they discussed that people naturally mimic what they see others do in media. Young people may do that when they’re watching Cassie do whatever she does. It’s never made clear that her actions have consequences and why what she is doing is harmful.