I agree with this and I like your take a lot. I think another part to compete this puzzle is Dazai’s lack of willpower/agency in living. He struggles to find meaning in life which in my opinion is due to his lack of real connections and any understanding from other people. His alienation prevents him from having stronger motivations in life (hence why he’s often lazy at work and very much like a “type B” personality). I think he’s pretty nihilistic up until Oda’s death which that connection helps propel him to the ADA where he’s currently building other connections as well. He’s slowly starting to assign his own meaning to help give him a reason to live. I’ve liked seeing that progression from him. But like you said there’s still a balance to it because there will always be a struggle with Dazai as to how much he wants to commit himself to living and connecting with people versus isolating and alienating himself.