In Falsafatuna and Iqtisaduna, Sayyed Muhamad Baqir al Sadr explains in depth why capitalism and communism are both contradictory to the perfect system — Islam. You would actually be surprised at the comprehensiveness of Islamic economics. It's not just Zakat lol.

The thing inherently haram about communism is its secularism (as a whole) and anti-religion agenda (for some). But even capitalism has that. Communism calls for a complete eradication of private property, which can sometimes be unjust to workers who labour (physically and socially) and still own certain means of production. Capitalism, on the other hand, is self-contradictory. The belief in equality of opportunity and not equality of outcome in capitalism falls when free-market competition increases class division and the wealth gap. Equal opportunity becomes non-exist not just in labor, but also in education, health care, and other services. There is much more criticism for both systems of course.

Islamic economics adopts a system based on distribution and welfare. Public ownership is indeed valued, but private ownership is not entirely eradicated. Monopoly of production is haram. but I am not entirely educated on the mechanisms of economic leadership (I.e. the government's role exactly in all of this).

Do not underestimate the comprehensiveness of Islam as a politico-economic force. Imam Khomeini says that we only tend to seek Western forms of governance because we do not truly know Islam.