As Chu Yu's direct creative assistant, Zhao Qinyin was the first person in this world to learn the plots of his works. But they were still only scripts, and the later storylines hadn't been laid out yet. She only felt that the plots of both works were fresh and captivating, and that was all!
As for Attack on Titan, the early story was actually more like a hot-blooded monster-fighting anime. The atmosphere was well done, but it wasn't yet at the level of a masterpiece.
But once the story began to unfold, with its worldbuilding, Erwin's death, and the various factions inside the walls and in Marley making their appearances, the work gained far more depth than simple excitement and hot-blooded action.
At the very least, many people in the Parallel World had criticized Isayama Hajime in the early stages of Attack on Titan for glorifying violence and gore and having a twisted sense of humor. But once the Marley arc began, the discrimination and treatment Eldians faced in Marley and throughout the world because of their history and race became clear. Even though Marley treated the Eldians there so badly, they didn't dare rebel, simply because other countries treated Eldians even more cruelly. They fought desperately only to protect their families in the internment zone, while also seeking to exterminate their own kin inside the walls. No matter how you looked at it, the story carried a mockery of war and an antiwar message.
Fullmetal Alchemist also took until the middle of the story, when the threads and foreshadowing surrounding the Homunculus, the military, the country, and the Philosopher's Stone began to unfold and the plot's pieces fell into place, for people to realize just how brilliant the work was!
But you couldn't truly appreciate the full essence of