Yes fanfic is a craft but fanfic writers also need to be willing to take criticism. Like you said, Some fanfic writers are good, some are bad, just like every other writer, but often what I find is that some fanfic writers crave validation and not real criticism. And if you do criticize their work, they say “it’s supposed to be fun!” Idk (and I’m saying this as someone who used to write fanfic)