I am from China. In my country, we don’t have many Creative Writing programs compared to US. We do have programs in Chinese literature, but they focus more on reading and literary studies rather than creative writing. But still, many Chinese authors have produced extraordinary works, like Yu Hua and Nobel Prize winner Mo Yan, my two favorite authors. They didn’t even finish middle school. While I personally know two Chinese authors who graduated from Chinese literature programs, their books are not well known or widely read.
I am not sure about situation in US, but for books I read, most authors didn’t come from MFA programs. I also have a friend who self published her science fiction who majored in Art. So that is another path to publication.
Based only on my personal experience, I do think MFA programs can be very helpful, but are not necessary. The focused writing time, the literary environment, and the opportunity to receive funding are nice, but many of these can also be developed through reading craft books and having a consistent writing habit