When Star Trek: Deep Space Nine debuted in Jan.1993, it was unlike any of the three previous series in the franchise. From the very first moments, it was clear the series was imbued with the same wide-eyed exploratory wonder that defined Star Trek: The Next Generation. It was seen as a dark and gritty take on Star Trek, for better or worse, but 30 years later, that description doesn't feel quite so apt. The show always had a hopeful, aspirational quality hidden behind how different this series was from what came before. When Star Trek: Discovery debuted in 2017, the first season kicked off a war between the Federation and the Klingons before jumping over to the evil, violent mirror universe.
Source：https://www.cbr.com/star-trek-deep-space-nine-darkest-series/
