I hate to read spoiler threads before I have seen an episode, but this episode is late on my Paramount+ app and I could not help but ‘peep’ .
If this is indeed an introductory series, then where are the Prodigy episodes involving Seven of Nine and the Fenris Rangers? This would make for a good backstory for the Seven of Nine spin-off. We could also find out why Seven of Nine and Janeway fell out.
I remember reading an interview with Kate Mulgrev in which she mentioned that she would like to bring the entire cast of VOY to Prodigy (so I suspect we could be given more dialogue on what happened to most of the VOY crew via Prodigy).
As for 7 of 9 and Janeway falling out... actually, that didn't happen.
In ST: Picard, Seven mentioned that Starfleet had reservations about allowing her to officially serve as a commissioned officer due to her Borg past, which stalled her application to SF academy.
Seven even mentioned that Janeway vouched for her extremely hard, and Janeway ALMOST had a falling out with Starfleet over the issue, but then Seven decided to withdraw her application and join the Fenris rangers instead.
As far as I know, Seven and Janeway didn't have a falling out... Seven simply chose a different direction, and probably kept in touch with Janeway via subspace.
It really didn't make sense to me that SF would discriminate against Seven over her Borg past.
She was assimilated at a young age without consent, and then went on to serve on VOY in a science capacity - and in the process, greatly helped the crew of VOY, helped push forward in regards to propulsion technology [slipstream etc.], and the crew also helped Seven finding her own path to humanity and individuality.
Given that Icheb was accepted into the Academy over subspace and was trained as a cadet on VOY, I have a hankering suspicion that had Seven decided to apply to the Academy with Icheb while VOY was still in the DQ, she would have gotten in at the time (because, back then, VOY still had years to reach UFP, and as such, SF wouldn't be too preoccupied with a former Borg drone having commissioned rank on a ship on its way back to the Federation - and having them on VOY as commissioned officers was useful to the ship/crew).
Something may have happened in between after VOY returned home and when Seven decided to try and join SF (we don't know when she actually tried to do so - but it seems to have been after the events of synths attack or something else related to the Borg that would have stopped SF from accepting Seven's application to the Academy, and since Icheb was already in, it would have looked bad to expell him - especially because he probably integrated well and didn't have a problem following SF protocols).
There's that, and the fact that Seven had some issues butting heads with Janeway and the command staff (which probably didn't go in her favour when making a face to face application). On VOY, SF knew she would have been working under people who knew how to handle her, so accepting her application over subspace while she was in the DQ would have likely worked.. in person/on Earth, she was an unknown and a potential disruption for the chain of command - at least, that's the way I tried to explain it.