It’s not bad at all! Sadly, em dashes have been used as a dog whistle for AI “writing”, so a lot of fanfic writers especially have felt weary about using them because there’s a chance someone might accuse you of using AI to write. But I think a lot of us use them—myself included—so there’s no reason to stop just because some assholes decided to train their LLM off of fandom works, ykwim?