The concept of universals is both wrong-headed and useless. Everything that is worth identifying can be without being force under another concept, "universal."
Which is to say that these “essences” are universals. A universal is claimed to be a really existing feature – or attribute, essence, quality, property, relationship, the exact term is immaterial – that is common to any number of like objects.
This is a perfect example of the uselessness of the concept of universals. Whatever you think "essences" are, the basic meaning is, they are whatever makes a thing the kind of thing it is. A banana is a banana because it has the essence "banananess," and a cow is a cow because it has the essence "cowness." Plato thought things like "banananess" and "cowness" were "real" things. Aristotle thought they were "attributes" that existed only in actual existents, but otherwise had no existence. The nominalists orginally thought they did not exist at all but were only names of things we (for who knows what reason) decided were the same. Of course that term now subsumes a number of different theories. Ayn Rand thought essence is just those attributes and characteristics (qualities) that were necessary for a thing to be what it is, and nothing more, but thought it was the identification of those qualities by means of a concept that made them essences. (I do not agree with that, by the way,)
But whatever you think an essence is, it is whatever determines a thing is what it is, and includes such concepts as human, mountain, dog, and book, the essences of which would be humaness, mountainess, dogness, and bookness.
Those who believe "universals" is a legitimate concept include these and all essences under that concept. Universals include all essences, BUT, they also include all attributes, characteristics, and properties of things. The problem with that is essences only determine the kind of thing anything is, but in addition to a thing's essence (or essential attributes common to all existents of that kind) they all have other attributes and characteristics. In classical logic these other attributes and characteristics, that are not a thing's essence or essential qualities, are called accidentals.
But if universals are essences, how can they also be accidentals, and what is the point of a concept that confuses the distinction between things? For example, human's come in an almost endless array of sizes, shapes, and colors. But human beings have other attributes. Some have good memories, others are forgetful. Some are honest, and some are dishonest. Some are serious and others quite frivolous. Since these are all attributes, they are all universals. So universals is a concept that subsumes humaness, redness, whiteness, forgetfuness, honestness, and frivolouness as all the same kind of thing. In what way are they possibly the same? Are they made of the same material, do they perform the same function, are all related to the same thing? The only possible thing that is the same about them is that they can be predicated of something. Well, we already have the perfectly good term, "predicates," which has none of the nonsensical implications of the pseudo-concept "universals."
Please explain one thing "universals" enable us to understand that we cannot understand just as well (or better) without that stupid concept.