After the death of her friend, Sito Jaxa (Shannon Fill), and her experiences during the Dominion War, Mariner rejected the idea of promotion entirely for fear of eventually having to be responsible for sending her friends to their deaths.

Source: https://screenrant.com/star-trek-mariner-wants-harry-kim-ensign-curse/

Helping assassinate a Romulan Senator was just one of the morally dubious decisions Sisko made during the Dominion War.

Source: https://screenrant.com/star-trek-dominion-war-crimes-sisko-cardassians/

Perhaps no other species lost more in the Dominion War than the Cardassians; they once sat at the center of a mighty empire, but they lost every bit of it thanks to the war.

Source: https://screenrant.com/star-trek-cardassians-hate-sisko-federation/

Perhaps the conspiracy theorists feel that Sisko has been disappeared to suppress information about his substantial role in the Dominion War.

Source: https://screenrant.com/star-trek-ds9-sisko-disappearance-conspiracy-great-story/

What seemed like a Changeling plot motivated by the fallout from the Dominion War for most of season 3 turned out to be an unlikely team up between the treacherous shape-shifters and the Borg.

Source: https://screenrant.com/star-trek-picard-finale-voyager-endgame-what-happened/