Dark vs Light Side

Star Wars focuses on heroes more than on villains. There are more usable and prominent light side characters than dark side.

You say not a single antagonist from KotOR, but KotOR 1 and 2 are pretty much a composite work. Looking at one without the other is rather splitting hairs. Saying we don't have a single antagonist from KotOR 1 is basically saying we don't have Darth Malak. But of the four principal antagonists of KotOR 1 and 2, Malak is the least iconic or interesting. And aside from being the only prominent villain to pull, the Sith really don't need more love right now, leaving Malak out of the anniversary celebration..

Meanwhile, crew members who haven't been added are Carth, Canderous, Juhani, Atton, Bao-Durr, Mical, Mira, Hanharr, Brianna, and G0-T0. Crew members not added to the game yet outnumber notable antagonists ten to one. And as these are Bioware RPGs, the game is mostly about going on dates with the bundles of trauma and neuroses you call a crew. Every character on that list is more prominent and developed than any antagonist. Yes, I'm aware two or three people on that list would probably be dark side. Still, the key antagonists are at 75% representation off of three characters, while the protagonists aren't even at 50%.

The rest of the dark side options from KotOR are B list, satellite or one-shot/arc villains, and at that point, you'd be drawing villains to a standard that would get Cham Syndulla into the game. Also, those villains like Darth Bandon or Carth's teacher dude are way less notable and therefore less likely to turn a buck.

For the Solo release, yes, Dryden Vos wasn't released, but neither were Beckett, Val, or Rio.

There are just so many more heroes to choose from than villains, because Star Wars is about the heroes.