A self-insert is a character the writer puts in the story who is indistinguishable from themself, often even having the same name. It is not the same as a writer giving a few of their quirks/idiosyncrasies to a character. Unless you're saying that every author who has every given a character a shared race, religion, sexuality, gender identity, disability, hobby, lived experience, hometown, fear, quirk, habit, favorite/least favorite food, book, subject, animal, or so on is writing a self-insert too. God forbid it comes to light that Karlach's writer is also fond of mutton.