For me, the appeal was having a full dex of fakemon (as opposed to blending the fakemon in with real pokemon as other fangames do). The big drawback for me was the humour; the issue with referencing memes in your game is that most memes have an expiration date, so playing through the game now causes the jokes to seem dated. Secondarily, a joke that falls flat on its face kills the immersion. Rather than seeming like a character saying something, it just reminds you that it's dialogue written by a 4channer years ago.