I liked that anime too. But I feel like the other characters need more development, because it has a large ensemble cast that you don't really know much about, and you're always wondering, "Who is this person?", "Why are they doing that?", etc.

And it's not the only anime where this happens; the same thing occurs in Solo Leveling and Kaiju No. 8. I see a tendency to reduce the depth of the characters surrounding the protagonist in order to make him stand out, and that makes the story feel too basic.