https://screenrant.com/star-trek-ds9-gets-good-before-worf/

The arrival of TNG's Worf heralds an improvement in the quality of Star Trek: Deep Space Nine (https://screenrant.com/tag/star-trek-deep-space-nine/) episodes, but I think DS9 actually gets better earlier.

Deep Space Nine is high quality from the start. Only season that isn't good is the final one when Ezri Dax replaces Jadzia Dax.