Here is a part of the criteria to be eligible:
"For an entry to be eligible for addition to AniList as anime, there should be significant creative control of the titles from Japanese studios and be professionally produced.
Even if a title was animated by a Japanese studio, it may not be added to the site due to significant creative decisions being made by western companies."
Let me correct myself, only being created by Korean Studio might be not enough if there is lot's of outside inlfuence. Below example from the Admission Criteria:
"The Legend of Korra was primarily animated by the Korean studio Mir, however, as it was produced by an American company (Nickelodeon) and the primary staff (director, writers, etc.) are also American, it would not meet our guidelines for an aeni show."