Production might be natural. Obviously consumption is natural. Trading goods, working for a payoff, and some forms of competition might be natural. But none of that means capitalism is natural. Here’s today’s quote:

Nature does not produce on the one side owners of money or commodities, and on the other men possessing nothing but their own labour-power. This relation has no natural basis, neither is its social basis one that is common to all historical periods. It is clearly the result of a past historical development, the product of many economic revolutions, of the extinction of a whole series of older forms of social production.
–Karl Marx, Capital