Why is createElement() a part of the Legacy API?

In the pursuit to learn React in dept, I am trying to understand how does React creating a component element. “Under the hood” it is using the createElement() method, and all of the “children” like html elemnts and attributes, are treated as props.
I wanted to read more about it and for example How it differs from Javascript createElement(), but on their docs page I see that is a part of the Legacy API. React Legacy APIs

These APIs will be removed in a future major version of React.

Does that mean they don’t use this method anymore, or won’t use this method alongside other APIs in the list? Or does this mean it is not recommended to use createElement() method in our app as a method of choice?

I have read the React documentation and googled, but I haven’t found an answer regarding the method in the context of my question.