From what I've seen, "Normie" is based on arbitrary criteria parroted by individual fandoms mostly regarding their own or others.
For example:
Back to the Future's fandom does not consider you a Normie for only watching the first film. To them if you like the first film, you're part of their group.
Star Wars on the contrary is such a picky fucking group. You're Normie if you haven't seen the original trilogy. You're Normie if you liked the prequels. You're Normie if you've never touched any of the extended universe. You're Normie if you like Star Trek for fuck sakes. They have this pride in themselves like it's some fucking secret club.
The Loud House. Holy shit, this is an even worst offender than Star Wars in its bogus labeling. Don't take to heart if you're called a Normie by this group because to them, watching the show isn't enough. You have to be comfortable with those horrid OCs, incest-shipping, drawn porn of any of the characters, fan fictions of incredibly questionable content, etc.
Basically, Normie is not used appropriately for mediums because the fandoms vary on what they consider "scratching the surface". They label you for stupid standards whether you're not even in their group or are.