One of the main problems with Aritomi is that he's too understated. He's not as emotional about this as he probably should be, in order to get a good sense of overwhelming jealousy coming from him. They're playing Aritomi as this really self-satisfied smug smart guy. They should be playing him as a bit snarkier, a bit angrier, much more emotional, a guy desperately trying to prove his worth. Instead, he comes off as mildly annoyed and calmly cynical, which is probably why a motivation that seems fine to me on paper isn't getting through well to some viewers.
Pretty much this. STUDY's personality doesn't reflect their current struggles. Aritomi, for example, just sneers at everyone with the confidence of a mad scientist. He may just be overly confident of his abilities, but his struggles as "a great mind that craves recognition" doesn't really show.
I feel like he was designed like a character that is perfect as a light novel character but was ported into the anime medium, causing most of his monologues to be lost in the adaptation. The problem is that he's an anime-original character. :/