For my major, Creative Writing, I have to take not only literature courses but theory and writing classes as well. When I get my BA, it will be in English with a Creative Writing emphasis, so I technically have to take the English classes that, say, a major in English literature would, but I will also be taking theories of writing and other writing classes, such as plays, fiction, and poetry. Those would be the upper division courses.
As for screenplay being a part of Creative Writing, it depends. It may be its own major, or it may be offered as a part of film studies. This depends on the college/ university.
The fiction class I took wasn’t about writing whatever we wanted: it was about how to construct a story and how to tell it well. My professor pointed out that not every popular book is written well.
He didn’t teach us to imagine a new world, but he taught us how to get that world onto the paper. Work-shopping was a major part of the class, so after we wrote our short stories or paragraphs, whatever was assigned, as a class we read each other’s works and gave constructive criticism. He pushed us to not write cliche genre fiction, but to present our world in our own voice and perspective. He also taught the poetry class in the same fashion.
Many of the past authors had access to literature that was considered part of the ‘greats’ in their time. They also practiced their writing, and they honed their skill. Jane Austen, for example, wrote skits for her family when she was younger, and she spent a lot of time in her father’s library. Charles Dickens worked as a reporter for a while. Shakespeare went to grammar school and learned the classic languages. Chaucer was familiar with the works of popular and famous writers in his day. J.R.R. Tolkien was a professor in Old and Middle English and a part of a literary group which included C.S. Lewis. The past authors not only had innate skill, but they had to practice to get better, to see which method worked for their writing, their era, and their audience. One of my favorite poets, Alfred, Lord Tennyson, was composing poetry before he attended school. He did, however, have a pre-grammar school education from his father.
Sorry if I seem to have rambled on, I got carried away