I've read the translated light novels. The story only picked up and showed the depth of the characters after the revelations in volume 5. This is common in the fantasy genre that needs time for world building and time to slowly build backstory. Seriously, I think the anime was only the beginning arc of the story (LN volumes 1-3). Its no surprise that the manga that barely covers volume 1 cannot show enough depth.
I estimate that around a hundred chapters from now, will we see that there are several enemies, much more powerful than the MC. Call them level 100. However, in the genre of battle mangas, the author needs to show enemies one level at a time. If the MC immediately triumphs over the strongest person in the world, that wouldn't be fun. The story will end quickly! We wouldn't be able to savor the battles with mid-level characters, at level 30 or 50.