The best libertarian left anarchism-compatible modern critique of capitalism has been put forward by libertarian left economist David Ellerman. He himself is not an anarchist, but his critique was cited in the anarchist FAQ. He also explains why capitalist economists defense of capitalism is besides the point.
A link to a short article where he explains his argument: https://www.ellerman.org/wp-content/uploads/2019/10/Council_DemocracyCaseForWorkplaceDemocracy.pdf
His book where he completely details his anti-capitalist argument: https://www.ellerman.org/wp-content/uploads/2012/12/Ellerman-Property-and-Contract-Book.pdf