I love Marx's writing but I wanna agree with you. Most of what he wrote was intended to be German academic writing. That is, solid, obtuse, and hard to poke holes in. He was actually a little more loose than the typical German philosopher of the time though, like he'd put in little characters like Mr. Moneybags or he'd talk about werewolves. I get a kick out of when he does that, he was pretty funny sometimes. He was also kind of a pedantic asshole and would preemptively try to anticipate contrary arguments and spend full paragraphs arguing with imaginary liberal economists.

Other times he was responding to other intellectuals in the newspaper, like his years long feud with Herbert Spencer. They also had a particular style.

He did write for a general audience sometimes, like the Manifesto is probably the clearest example. He also worked as a journalist for the New York Tribune. I can recommend reading his articles about the Crimean War as it was happening, they're pretty standard and easy to follow.