The alternative is everyone grows their own food, builds their own houses, makes their own clothes, gathers firewood, yadda yadda.

You certainly wouldn’t have the Internet in such a paradise.

That said, with all that we now have, 4 6 hour work days should be the norm.

You should not confuse capitalism with markets, and you should not confuse markets with working together.

Consider the family unit, it is doubtful that everyone cooks their own single serve or rotates meal duty evenly. Humans can specialise without capital.

Capital is what enables someone to have someone else cook for them, who then has to go cook their own meal. The one with capital isn’t even doing anything for the cook, they are simply taking money that someone working at a widgt factory they own made and giving it to the cook. In so doing they appropriate both the widget factory worker’s meal and the cooks!

you can even have market exchange without capitalism. In the above situation if we remove the capitalist the widget maker could give the cook widgets for a meal. Or even currency from selling widgets for a meal. Materially the capitalist contributes nothing, their role is entirely created by private property law.