‘Class,’ as a word, has been used for longer, more commonly, and more recently, to mean a group with a shared quality. Class is like energy; both words are rather meaningless alone and need a specifier to make them useful. Just as energy can be thermal, electrical, or various other kinds of energy, but referring to energy in general is usually not sensible, one can be of a socioeconomic class, a protected class, a school class, the managerial class, a or various other kinds of class. Only the very narrow class of people who have taken a class on a bit of Marx but not a class on the classes of words used by classmates in classes on English or Programming think ‘class’ can only refer to ‘class’ delineated by socioeconomic relation to the mode of production. Ol’ Karl didn’t invent the word. He used one that already had broad use.
Simply put, reading.
Reading has a powerful effect on the brain. It trains it to maintain focus and coherency in thought. It trains the imagination to allow more complex visualization. It trains it to hold more information in working memory. It can be used to add cognitive tools that allow for more advanced/nuanced forms of thinking. It’s a superpower we forgot because someone found a way to take photographs. Go read something. I’m going to go read right now.