The thing about ritsu is that his disability, while not being his entire character, does still impact every part of him. His symptoms presenting more strongly is why the sakuma clan valued him so much less than they did rei. It's the basis for his family's dehumanization of himself and their entire clan. It's part of why he became so isolated from everyone around him, because it physically made it harder for him to participate. It affects the way most of the other characters see him, making them label him as lazy and spoiled instead of a guy that just needs more assistance than most people, and he quickly latches on to the one single person outside of his brother who cares enough to give him that assistance (even if he too complains about him being lazy and spoiled over it). Rei left him specifically to look for a way to cure him without ever asking if that was what he wanted. He sees it as something that he has to "overcome" in order to be accepted in the "human world". I could continue
Basically what I'm saying is, ritsu's disability is a HUGE integral part of his character and if you choose to ignore it or boil it down to "he's just an eepy little guy" regardless I will maul you
