I didn't say capitalism is about being evil. You just blatantly lied about something I wrote, invented a false quote out of whole cloth, and are confusing a system with an individual action.
When you state, "Capitalism is a system where socioeconomic power can be sold and bought in the form of 'capital'," you are basically defining it as "a system where an individual can do X." No, that phrase is itself incoherent, because systems are not defined by what individuals can do, they are defined by what the system actually does. That is to say, to be capitalist, then the defining characteristics of capital accumulation, i.e. commodity production and the extraction of surplus value by the capitalist class, has to be the dominant mode of production in that system, in the real, physical world.
You are using idealist definitions whereby a "system" is defined by what is written down on paper, and not what exists in real, physical reality. This is a flaw many liberals like yourself have: seeing things in terms of legislative ideas and not what physically exists. It is nonsensical to define a socioeconomic system in terms of potential individual actions allowed for on paper, but they instead have to be defined in terms of the real-world dominant structure of the system as it exists in reality.
Blatantly lying and claiming this topic somehow had anything to do with moralism" and calling someone "evil" doesn't make your "definition" any more reasonable.
Your idealism stems from liberal philosophy in general. Liberals are historical idealists, they believe in human "free will" and if individual humans have free will, then surely, a collection of humans, i.e., society, has "free will," and thus society has the "freedom" to choose whatever it wants to be, regardless of material circumstances. You thus have a hyperfocus on understanding systems based upon the ideas and ideals written down on paper by the people who run it, because that is ultimately seen as the determining factor for the whole system.
But that is not how Marxists see the world. Human societies are physical machines built in the real, physical world, built upon real material circumstances. These unconsciously dictate the structure of the basic structure of that socioeconomic system, and the legislation that is later enacted is only there as post-hoc rationalization for something that already, for the most part, pre-existed.
The aim of political economy, then, is to objectively study these physical structures as they arise, and to document them as they really exist in the real world. The ideals and morals of the leadership of a society in what they write down on paper or legislation or say in their speeches is not of primary concern. The primary concern is actual material system that exists in the real, material world.