I hate the phrase "true fan" and i feel like people use that phrase to gatekeep people from enjoying something.
I can understand loving something, but when someone starts saying "only true fans remember this episode!" and other crap, that's when it crosses the line for me. I don't really wanna be a true fan of anything, in fact, i don't even believe anyone can be a true fan of anyone or anything, i feel like people only use that phrase to raise their egos and make themselves feel better than others. Either way, just liking something is good enough in my opinion. Just don't think you're better than other people and fans. "True" fans also prevent newcomers from enjoying something and bully people for not being knowledgeable as much as them. One has to know that without the past, there wouldn't be future, everyone starts at some point.
Yes, it's true some people are very good at games, sports, running etc. But they weren't always skilled, they either learned from someone else or by themselves. People can't be good at everything.
It's ok to be a fan of anyone and anything. But "true" fans can be annoying and rude.

Enjoying things is not a competition. You either enjoy things or you don't. Some people know less, some people know more, but it's not a competition. It's an entertainment purpose.