#you can't study and do research 24/7 from childhood

[another-goblin]

Why Ratio isn't in Genius Society - theories

Nous regarded him and decided that he's doing fine without them.

Or because he isn't a genius. When he calls himself mediocre, it isn't a humblebrag. He's just a normal human with average intelligence. He achieved everything through hard work (in one of his character stories, his old professor talks about how, even as a kid, he'd wake up very early, exercise, and spend the whole day studying).

That's why he's often frustrated with his students. Like, guys, you are provided with all these opportunities to learn, you can surpass me, why are you squandering them? Or, I sacrificed my childhood and youth to science, why isn't everyone else willing to do the same? (turns out most people only become students to finally enjoy adult life away from their parents and maybe acquire some minimal knowledge and credentials to have a chance of a cushy job in the future.)

BTW, as a teacher, isn't he a self-made emanator of erudition? Not in a mystical Aeon-related sense, but literally—he spreads knowledge.