In the long term it is. Capitalist by design favors the individual. That’s not inherently a bad thing, until it comes at the group’s detriment.

Humans evolved as social animals; attaining personal benefit from the group’s success is both normal and optimal. If the group has more food, everyone is stronger for it, which means the group can get even more food as well as better defend themselves. If one individual hoards the food for themself, the group is weakened, losing the capacity to obtain more food or defend its members, which puts the food hoarder at risk as well.

Capitalism encourages and protects the food hoarders. It’s not “i need to make sure the rest of my group also has food so they can protect me,” its “if the rest of my group isn’t also hoarding they deserve to starve.” Instead of “I share my food so we all have the strength to get more” its “I give them some food so they can get more for me.” It’s unsustainable. No other social organism lives like that.