The fact that the poor still exist in your ideal “fair” society indicates that a capitalist system still relies on exploitation. How do you make “work or starve” disappear while still being capitalist?
Communism is a stateless, moneyless society. It’s a utopian marker for people in the present day. It’s not a fixed ideology in and of itself. The Spanish Anarchists of the CNT-FAI and the USSR have very little in common but both aspired to implement communism, at least on paper. I have my criticisms but they’re not relevant.
You would be correct in saying that people have an innate desire to labor and improve their lives. Capitalism forces you to (attempt to) improve your life and shape the world through competition with your peers. If you’re disadvantaged in some way, fuck you. Work harder or die in the streets. Social programs and welfare are antithetical to capitalism. It doesn’t independently generate profit and thus is often ignored or slowly eroded over time when it does manage to manifest. Socialism/ socialist ideologies (worker ownership of the means of production) enables people to improve their life and shape the world through cooperation. It seeks to ensure everyone is able to live a dignified life and contribute according to their ability. Humans are capable of both competiton and cooperation and capitalism builds a very one sided society that demands competition. It’s a terrible way to live and alienates people from each other.
Socialism (in my perspective as an anarchist) seeks to allow people to live their lives with the maximal amount of freedom, self determination, and autonomy possible. Whether that includes markets (which I’m assuming is what you mean by capitalism, since that’s what most people who defend capitalism think it is), planned economies, gift economies, library economies or something completely different, is a better system than capitalism on a foundational level