When we use the word “abstract”, we generally mean to say that it makes logical sense but lacks a connection to anything real. In this sense, “abstract painting” is a misuse of the word. It’s true that an abstract painting does not point to anything real but it’s because the painting itself is the beautiful object. The term is misleading in that it implies it is still a pointer, or a sign, that happens not to point to anything.
In fact, very few things are truly abstract. For instance, for most people, music theory is abstract. Even if they can understand it theoretically, it would feel abstract, especially if they don’t play any instruments. But it does not mean that music theory is inherently abstract. It’s only abstract to those who have not developed an intuitive sense through physical practice. Something being “abstract” is subjective.
Historically speaking, for most subjects we study, theories came after the fact. When we study any new subject, we tend to start from theories. This leads us to believe that theories came first for everyone. This is partly why many people struggle to understand abstract works of art; because they go in head first, instead of allowing themselves to just experience them first. Having nothing for their brains to process throws them off.