If Marxism is a science, then it must be testable and falsifiable. At least, that's my understanding of the scientific process. It's why Freud for example is considered unscientific. This theories have a lot of wiggle room, where any result can be turned into a proof or explained away.
Isn't this what we do with the various leftist projects? I don't know, I'm just confused why it is called a science and not, like, philosophy.
Thank you, this clears a lot of things up. One quote from what you linked that really helped was:
I had always read that a product isn't a commodity unless it is socialy useful and can be exchanged but I was still unclear of its implications and how it refutes this mechanical idea of value.