Is no one going to talk about the fact that you are a human child living in a town built by anthropomorphic talking animals who also don't seem to age? Tortimer is the only one who shows any sign of age. Blathers and Tom Nook too, via familial relationships, but that is unconfirmed.
That doesn't even include the fact that Main Street was built then went to **** with Tortimer in charge. What kind of creepy stuff was that old man preoccupied with? Is this why Isabelle never goes home? What will she find there?
Anyways...the most unrealistic thing is definitely the talking animals.