Meh endings are a very common problem with the genre, not exclusive to AoT. It's very hard to find a good Shonen ending that managed to please everyone. : r/ShingekiNoKyojin

Anime Recommendations Thread - Dollars BBS

Nasuverse Discussion Post – Dragon Quill

Translations & Betrayals

Nasuverse Discussion Post – Dragon Quill

Mahou Sensei Negima! – 3-A Forever (END) – Random Curiosity

Anime Recommendations Thread - Dollars BBS

What do you think Eren's true plan is (Attack on Titan Manga)? - Quora

Will Attack on Titan Have An Anime Original Ending? – In Asian Spaces

emoetion/data/Bakuman. 3 at master · Havaldar/emoetion · GitHub

Calaméo - SGcafe-Cosplay-Anime-Manga-May13-s

MangaReview: (AoT) The Mediocre Ending for a Monumental Epic.