This assumes that people are naturally and totally individualistic, which is untrue even at a biological level. People work together instinctually, and they also decide, rationally, to work together. Individual and collective motivations are often the same; and while collective motivations sometimes stifle individual motivations, the former often (if not more often) replaces a LACK of motivation. In fact, the appeal to engaging in collective action in order to fill in a hole of individual meaning (motivation) underpins some of humanity's strongest and most common institutions: military service, volunteer service, protest, religion, work. That is society: individuals working in concert, by each's determination.
>I'm making 0 moral judgements on whether the motivations of an individual are or are not valid.
You're making a moral judgment privileging individual motivation, separating it from collective motivation.
Your argument is simply wrong on its face. It tries to generalize a solipsistic perspective to the rest of humanity, to which it very clearly does not apply. Perhaps only in this thought are you truly as much an individual as you seem to think people must necessarily be.
I share the same argument David Graeber was making in Utopia of Rules, you should give it a read.
Read "The Selfish Gene".