There are other types of antagonists besides people.
We love stories where we can recognize a person, a character, that our hero must fight and overcome. It makes it personal. And we like personal.
“He was a good cop. They killed his partner. Now it’s PERSONAL.”
But the antagonist of your story doesn’t have to be a person.
It could be a test or a challenging situation or a disease or a math problem.
Sure. A math problem.
But whatever your antagonist is, the same rules apply. Even if it is a math problem, it needs depth and character. What kind of math problem is it? Why is it so difficult? Does it unlock some secret? Is it the hero’s father’s greatest failure? The math problem should have history and meaning, just like any great antagonist.
You can be really creative with this. Or layer antagonists. Think of the end of Indiana Jones and the Last Crusade. We had the Nazi antagonists, who shot his father, which means that Indy needed to move through the obstacle course (each obstacle a mystery with spiritual meaning) to save and heal his estranged and eccentric father. Do you see the different layers there? In one act, trying to get the Grail, Indy was fighting the Nazis, fighting to save his father, and fighting the mysterious and allegorical obstacles. Each had depth and character even if not a real person.
Whether your antagonist is an object or situation or a person, your story will connect with people when you give it meaning and depth, when it is personal for the hero or protagonist.
Peace.