I see Legacy as Trek's answer to Better Call Saul.
Seven is a former Borg drone. She was evil incarnate for eighteen years.
She's killed and enslaved. She has a history of doing VERY bad things (she came thisclose to going back to the Collective in Picard S1). She's now trying to go straight.
For eighteen years, Seven ate, breathed, and slept evil. She's unlike any other Captain of the Enterprise that's come before her.
That's something worth exploring. She has one of the most complicated psyches in all of Trek.
And it’s precisely this complexity that has me wondering why Seven’s journey involves her being back in a Starfleet uniform.
She’s been a part of the Borg Collective for 18 years. But she’s also been a part of Starfleet (4 years on Voyager, plus a 1 year period on the Stargazer/Titan), and the Fenris Rangers (15 years), with a number of the later years being ostracized from Starfleet life for being Borg.
Yes, she did a bunch of horrible things as a Borg. At the same time, would she have done those horrible things if Starfleet denied her parents access to a ship?
B’Elanna had trouble adapting to Starfleet standards, and she went through the Academy (she said so herself). Meanwhile Seven, with her breadth of knowledge that she gain from being a part of the Borg Collective, is going to excel within Starfleet no problem. A Starfleet that has been traumatized by the Borg, again?
The same Starfleet that did nothing to bring Icheb’s killers to justice? Who she treated as a surrogate son?
The same Starfleet that let Picard go off on his own while looking for Soji, because they refused to help him at first, despite him being a Starfleet icon?
The same Starfleet that gave up and walked away from the Romulan supernova evac?
And keep in mind, she had an idea built into her head as to what Starfleet would be like once Voyager returned to Earth, thanks to Janeway and the rest of the crew. And also had to rediscover her humanity outside of Voyager upon their return to Earth. And found out that there is no room for mercy in the galaxy.
That’s a far more complex world view than someone that dreamed of Starfleet all their life like Picard, or even being caught between Starfleet and an alien culture like Worf. Seven’s worldview is unconventional for Starfleet. Seven has enough knowledge and experience to know that Starfleet isn’t the only way to leave a positive legacy.
This is something that Chabon and Goldsman got right, and Matalas got wrong. That Seven’s story, and what her legacy will be, lies outside of wearing a Starfleet uniform.