Read an interesting comment by Ira Steven Behr recently; he was talking about whether or not Bajor could or should have joined the Federation at the end of the series:
It was the mandate at the beginning. And as we went through years of doing the show and the multitude of episodes, it was like, ‘Why does Bajor have to join the Federation?’ Why is that the be-all end-all? Why is that the success story? Isn't it more interesting if what happens isn't said? They come to us. We come to them. And our captain becomes a god. And when someone told me that in one of the novels Bajor did become a member of the Federation, I thought, ‘Man, they don't understand Deep Space Nine at all".
https://uk.ign.com/articles/2019/05/10/what-star-trek-deep-space-nine-left-behind?page=2
It was the mandate at the beginning. And as we went through years of doing the show and the multitude of episodes, it was like, ‘Why does Bajor have to join the Federation?’ Why is that the be-all end-all? Why is that the success story? Isn't it more interesting if what happens isn't said? They come to us. We come to them. And our captain becomes a god. And when someone told me that in one of the novels Bajor did become a member of the Federation, I thought, ‘Man, they don't understand Deep Space Nine at all".
https://uk.ign.com/articles/2019/05/10/what-star-trek-deep-space-nine-left-behind?page=2