There's a very long list of things that would be different with DS9 if made today instead of the '90s.
Openly genderfluid, non-binary, and trans characters would be a part of the show. And it would not just be exclusive to humans either, Trill, Bajorans, Vulcan, even Klingons would be in on the fun. Poly relations would be more open and accepted as well.
Bashir and Garak would openly be a couple; there would be no hidden subtext, meaning no Garak-Ziyal relationship. I think that it would be relationship between Miles and Bashir that fans would wondering if there’s something more there, instead of a close friendship between two men
The relationship of Miles and Keiko O’Brien would be seen as odd; specifically, that there’s conflict in the relationship at all and they still stay together though everything. It would be expected that they either break up, an infidelity is involved at some point in the relationship (physically or emotionally), or they just don’t argue and have a peaceful and cooperative relationship.
Sisko’s story, even if the grieving over the loss of his wife was kept, wouldn’t be about his involvement of the Prophets and being the Emissary. It would be which side is he really on (i.e. the bigwigs of the increasingly authoritarian Federation or the people that live within the Federation), and the various structural changes he failed to make when he was once in a position of power (i.e. on the Federation Council), and why and how its led to cynicism within the Federation. With Jake, it would be how the messages of his father’s generation does not resonate with his, and it would be the source of distance between them
Kira actions would be treated like she was a part of the Rebel Alliance, meaning the complexity of her actions during the Occupation would be eroded. While a terrorist faction like the True Way would become 24 villains, and it would be more about the urgency of preventing an attack rather than exploring their motivations. The Maquis would be treated as Antifa, resisting the Cardassians and Dominion without assistance from the Federation; an action like Eddington attacking the Malinche doesn’t occur in the show. We’d probably see Section 31 try to internally break up the Maquis out of fears that they will turn against the Federation.
Nog’s PTSD story probably takes a darker turn, with PTSD explored among several officers, with a few of them taking their lives or the lives of others with them.
“Field of Fire” probably lasts several episodes, possibly the whole season. Meaning a whole season of Ezri being morally and psychologically conflicted in exploring the darker hosts of the Dax symbiont.
Dabo girls would be given a more feminist presentation i.e. Quark’s bar would be owned by a female Ferengi and the women are no longer there for the male gaze. The Vulcan Love Slave holosuite program might even see a genderswap in usage.
The Prophets would not be central to the conscious of the show. Or if they were, it would be a far more critical look at religion (fanaticism within religious structures, televangelism, erosion of the separation of church and state, miracles and divine intervention in the wake of major disasters or tragedies). Klingon religion would also be more criticized heavily, the Founders in the Dominion would not be worshiped by the Vorta and Jem’Hadar the Dominion would be led by the Karemma and the Dosi), and critiques of religion would even call back to TFF and Sha Ka Ree. The community aspect that religion provides would be treated as a secondary aspect. This would probably mean a show where the station is located somewhere else, far from Bajor.
On the flip side, the rise of the Cardassian Union and its expansive and pervasive influence in Federation colonies, along with the actions of the Obsidian, Order, Tal Shiar, Section 31 and Klingon Intelligence, would be more thoroughly analyzed. How intelligence is gathered and used, and how the accused are treated within judicial systems would be more explored.
There would be a more thorough look as to what happens when the oppressed becomes the oppressor i.e. Bajor picks on a fledgling world that is very similar to them.
A more critical look at the Federation-Klingon alliance, with Klingons behaving more like a rogue state killing dissidents within the Empire, and actively undermining the Federation’s political structure. “In the Pale Moonlight” might even be done from Martok’s perspective, instead of Sisko’s; not about protecting the Beta Quadrant, but the Klingon Empire.
We’d see a Ferenginar that is more openly favourable to 21st century Earth,, glorifying several business leaders and politicians in the process, and see nothing wrong with the problems that Earth faced during the period. 21st century Earth would be seen by Ferengi as the paradise that humans left behind.
Much would be made about how Starfleet warp engines have significantly threatened the fabric of space, making several M-class world unliveable and created more Badlands-like environments in the process, with a push for cleaner warp drives; everything from slipstream to the Romulan’s singularity drive to solar sails would be on the table and explored.
There would be more fear about androids like Data and holograms like Voyager EMH replacing humans and other species the workforce and in their personal lives. And in turn, the holosuites would be treated with controversy, as would exocomps.
It would not be shy to address mass murders in traditionally safe places like schools, churches and malls, using M-class world within the Federation as allegory, and get to the root causes of such events.
The Federation President, instead of the Bajoran Kai, would be the central political figure that makes recurring appearances throughout the show.