philosophy

In general, Marx mainly focused on criticizing capitalism and liberal ideology. He didn't particularly elaborate on projects for a future society, as he believed it was impossible to predict. The main points of Marx's criticism are:
1. Under capitalism, the market satisfies not needs, but demand (i.e., needs backed by money and imposed by advertising).
2. Under capitalism, there is a complete alienation of the individual, both from their labor and from their own personality; everything is subject to the laws of the market.
3. Capitalism has a beginning and, therefore, is finite, not eternal and infinite.
That's the gist of it.