Desire and technique
Only two things are needed to make great novels, or perhaps any great art. They are desire and technique.
Technique gets talked about most. How well a writer uses words to be beautiful or powerful or funny or clear. Most writing has poor technique, but good writing is not rare. Thousands of English speakers write well, in a variety of styles.
Desire is not talked about enough, the desire to do something particular with your writing. Often writers desire more than one thing, and different desires sometimes react with one another. A novelist who wants to please their readers may cut forty pages about loneliness for fear that no one will stay interested that long. A novelist who wants to express their loneliness to its full extent may put them back. The same novelist can be each at different times.
Since roughly 1900, novelists considered literary have often suppressed their desire to please readers, or haven’t felt it in the first place. This makes superficial sense, because it seems to ensure the honest expression of their other, more interesting desires. Novelists who do not shape their work to be liked are seen as purer and better artists.
But they are neither. Because in a novel, failing to please readers is poor technique. A good writer who does not want to please is almost always making a mistake by producing three hundred pages of prose fiction, which require hours of sustained enthusiasm in order to be read. They get some support from a puritan caste of readers who claim to enjoy persisting through dull novels, and from another caste who claim to find delights that are invisible to the rest of us, but I doubt the truth of both.
Furthermore, and more importantly, impurity is human. It is dishonest to try to make your writing purer than yourself. Most great novelists wrote at least partly for success in a censorious world, and their honesty escaped regardless, sometimes in ways that only other people understood.
I think readers of literary novels are often bored and not admitting it, even to themselves. In a very small number of cases - Kafka is the only case, for me - a novel can be hard work, yet wonderful. More often, I find admired modern fiction aimless and inconsequential, shaped above all by a desire to look like literature.