Artificial scarcity from landlordism and usury on credit are still enormously important, but IP arguably even more so because knowledge and technique result in less dependence on land and capital.

Many of the classical anarchists came out of the republican tradition for this reason. Pernicone and Ferretti have done a great work exploring this type of development in Italy.

And another thing, to pitch the left right divide, in the French Revolution, as only a matter of state affairs is simplistic. A key difference in the split was over social relations. The republicans, minimally, were advocating to flatten them whereas the right/conservatives advocated for hierarchy.

Embracing multiple tendencies is important and necessary. But to argue that anarchism was not historically left wing is dishonest. If they want to advocate for post-leftism, have at it. That said most historical/classical anarchism sat firmly on the left (except the Stirnerites).