Because it’s 'creatively' not an anime.
Even thought it’s animated by South Korean Studio Mir, it has majority Western creative control… just like The Legend of Korra and The Boondocks also animated by Mir. The producer Adi Shankar does a bunch of anime-influenced shows (that Netflix likes to call “anime”) but are not technically anime as not produced with Asian creative control.
Animated Media Criteria/Anime - Submission Manual
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.
Example:
Rejected Submission
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.Animated Media Criteria/Frequently Rejected Anime Titles - Submission Manual
• Devil May Cry (2025) [Producer: Adi Shankar, Studios: Studio Mir/Netflix] - Reason: Not an anime.
What about Chinese animé like to be hero X?
I was abridging the criteria wording… we do list aeni for South Korea and donghua for Chinese/Taiwanese animated works, with the same wording as the Japanese anime rule, except with their respective countries.