The OP is confused about the difference between Marx, who didn't believe in a system built around private property, and Keynes, who most certainly did. This kind of confusion is common among those with limited post high school education, leaving them victim to things like talk radio and popular media.
Democrats side with Keynes in their belief that markets generally get incentives right, and they do a better job (than government) at calibrating supply and demand. However, they believe that markets are fallible, and subject to corruption and terrible crashes. For this reasons a Keynesian believe in regulations along with government stimulus during downturns (which actually includes tax breaks). Keynesians also favor infrastructure projects so that capital investment has the advantage of modern transportation, energy grids , water works, disaster relief, and technology, e.g., the satellite system or the technology that came out of the Cold War Pentagon/NASA, for instance.
Most Republican presidents have been Keynesians, though the post Ford Republicans (Reagan/Bush 41/43 ) didn't admit it. Reagan added more government jobs than any president thereafter, mostly in defense; and he also funded massive defense sector technology which has had profound commercial applications. He saved Social Security. Bush 43 used his ownership society to stimulate a housing boom, which had an immense economic multiplier effect. He also made the largest expansion of the entitlement system since LBJ with his Medicare D. These are just a few examples.
You might research how the government defense jobs Reagan added in Southern California stimulated the economies of that region. Each government job represented another consumer on Main Street. Reagan may have been rhetorically against big government, but he was a brilliant military Keynesian.
But here is the point. A socialist does not support markets at all whereas a Keynesian believes that government can partner with markets - and nobody proved this better than Eisenhower, Nixon and Reagan.
You might say that Keynesians are closer to Socialists than Libertarians, but to confuse Marx with Keynes makes you sound like an idiot. There are huge conceptual differences.
(This is why Trump is leading in the polls with Republicans. The Republican Party needed the under-educated low-information voter to create an electoral coalition strong enough to topple FDRs New Deal coalition - and now we are lying in that bed)