I don't think anyone has a moral imperative to read theory, just as learning about any other topic isn't a morally good or bad thing to do.
But the political, social, and economic organisation of our world impacts every aspect of our lives. Most people here understand this, understand that morality cannot really be separated from politics in any meaningful way.
So, very often, people will attempt to figure out how things work. To talk through what they think is going on. And what they're doing, is theory. The texts people currently describe as "theory" are mostly doing that, trying to figure out how stuff works and what is and isn't true, and what we ought to do about it.
More often then not, people who aren't very familiar with theory, will end up voicing existing theoretical ideas. That's not a bad thing! I think it's impressive and it makes me feel very optimistic every time I see it happen.
Marx has this idea, that workers, unlike those who exploit them, have an intuitive understanding of the way things work, because they live that exploitation every day. In a way, when people say "I don't need to read what old white men said, I know how I'm being exploited", they're saying a bit of Marxist theory. I don't think that means you have to read Marx. I don't think that means you shouldn't read Marx. I just think that's neat.
But why is theory so hard to read?
Part of this is absolutely just because some of these texts are old. But there is also another reason.
So, theory tries to explain how things work, right? And, most people think, that the world is quite complicated. So you end up having to wrestle with big complicated concepts. And then you have two options.
Either, you write extremely long and weirdly structured sentences to convey these complicated ideas (for example, putting "our current mode of producing things, which has X characteristics" in a sentence).
Or, you use long, unusual words, that look confusing and ugly ("capitalism").
And there's another aspect to this. Theory tries to figure out how things work, right. And there's a whole group of people who don't want you to find out how things work. And they create these false ideas about the world, and spread them. And it infects our language. In other words, it is difficult to describe the way things are in ordinary language.
Often, you will try to articulate what they think is true about the world. And you might struggle to express it in a clear, straightforward way. That's not because you're stupid or bad at expressing yourself. It's because your language is designed to prevent you from describing things as they are.
One of the theory books that I've found the easiest and most fun to read is Mark Fisher's Capitalist Realism. In it, Fisher complains that his students ask for a simplified summary of Nietzsche. What they're missing, he says, is "that the indigestibility, the difficulty *is* Nietzsche."
Do things have to be difficult to be true? Or can simple statements, that are easy for anyone to understand, accurately describe the world as it currently is?
I don't think I know enough to be the judge of that.
It is absolutely possible and Marx's work has been dissected into simple statements many times - e.g. by Leszek Kolakowski in "Main Currents of Marxism".
The problem is that when dissected and stripped of the cryptic language, many fallacies of the Theory become obviously visible... but if you're a believer this is the last thing you want, so the only recommended way of ingesting is total submission to statements of the original text.