I don't think the problem is that theory is too hard to read. Most people can read difficult texts, especially if they're annotated or if they read it in small chunks. The bigger problem is that most people are just not in the habit of reading books.

(Of course, I realize some texts are more difficult than others, and I don't want to dismiss other people saying they're having difficulty. OP, is there a specific paragraph you have in mind?)

What I'd love -- and I know this sounds like a bad joke, but bear with me here -- is an app that takes classic works of theory, divides them up into readable chunks, maybe gives you a quiz after each chunk to test your comprehension, and keeps track of your progress. You could earn streaks by reading a few pages each day. Maybe it arranges texts so that it starts with the easy stuff to introduce you to concepts (e.g. start with the Manifesto, maybe some Lenin), then gradually introduces more difficult readings over time. You could have a cartoon mascot with a Karl Marx beard to give you reminder notifications every day, like the Duolingo owl.