When PS was approached for the new series, he was the one who set down the mandates that distanced it from TNG. He didn't want any of the original cast. He didn't want to be in Starfleet or wear a uniform. If they were bringing back Picard, it had to say something new about him rather than re-explore old ground. I actually think there was a lot of merit to these stances, even if all we really wanted was a TNG reunion, which we eventually got. But I don't think S3's reunion undermines the rest of the show, nor do I see it as a retreat. It's a necessary conclusion for Picard.
Think about where Picard was at the end of TNG. He just had his Christmas Carol-like jaunt through time and came out realizing he needed to change the nature of his relationship with his crew. He joins the poker game. He's on his way to becoming less distant. He's opening up... And then what happens six months later in GENERATIONS? His brother and nephew are killed. He's the LAST Picard. There IS no biological family left for him.
And then what else happens? He meets Starfleet's greatest, James T. Kirk. And what's the retired Kirk's firm advice?
"Don't let them promote you. Don't let them transfer you. Don't let them do ANYTHING.... that takes you off the bridge of that ship because while you're THERE.... you can make a difference."
Taken together, we see how this pretty much cements the crew of the D as his family.
And over the course of the movies, that changes. It can't last forever. Worf leaves the nest and moves on for a time. Will and Deanna get married and go off on their own. Data DIES. Beverly leaves.
Then comes the whole Romulan crisis and then the android revolt. Picard's at the center of that crisis and Starfleet fails him. After an android sabotage of the shipyards built to evacuate the Romulans, Starfleet scraps the whole project and makes artificial life illegal in the Federation. It goes against everything Picard has fought for. By then, most of his "kids" have moved on. He took Kirk's advice. He stayed devoted to Starfleet and it fucked him in the end. So he quits in protest.
He doesn't recognize Starfleet. Problem is, without Picard - who had no bones about standing up to them in cases like INSURRECTION - Starfleet loses its moral way too. And that's where PICARD the series picks up. Picard's lost his family and the thing that was supposed to matter.
When he has to go on a new adventure, he's determined to do it without getting in the way of the old crew's new lives. This is JLP in his "Wings" phase. (The Enterprise D/E era being his "Beatles".) And look, Wings was a fine band. But they weren't the Beatles.
But step by step, PICARD shows us its title character putting things right. The android ban is lifted. He goes back to Starfleet, beginning to restore its moral center. S2 at first glance, can be mistaken as a bit of a sidequest. Q messes with history to create a timeline where Starfleet is a totalitarian conqueror, which forces Picard to go back in time and try to put things right.
Eventually it's revealed that history hinges on one of Picard's ancestors going on a crucial space mission. The ripple effect of her not going is what would result in the imperialistic Starfleet. What this means is that the moral fibre of Starfleet is inextricably linked with the Picard bloodline. Starfleet and Picard inform each other.
Just as The Sisko is of Bajor, Picard is of Starfleet. Starfleet is what it is because of the Picard family. In Starfleet, Picard found his family - both in spiritual and literally biological terms by the end of the third season. That is the lesson that Q is trying to teach in season 2. Why else show him that?
Picard needed to rediscover Starfleet as being core to his destiny so that on the final adventure, it plays out the only way it can for Picard to truly come full circle. The lesson he's been learning for 30 years finally is achieved.
His old crew IS his family. Of course they are the ones he ultimately has to take this last ride with. And for his full restoration, is there ANY other ending that could be more perfect than him leading the charge to save all of Starfleet with those people by his side?
And if you're putting all The Beatles on stage together, what madman would do that and NOT having them perform?
Kirk insisted that on "the bridge of that ship.... you can make a difference." It HAD to be the Enterprise-D. These seven people had to be by each other's sides one last time, willing to die for each other because if not, what were the last 35 years even for?
For Picard's arc since the series - the man who lost his blood family, lost his ship, lost his friend Data, lost his faith in the institution that was supposed to be his life - he gets a new family. He gets back the ship and the friend that he lost and he restores it all. Yes, I know.... every brick on that road was laid individually, with no real plan of it leading all the way to this path for much of it. But when you look back with hindsight, it all makes so much sense. PICARD S1 and 2 had to happen to make 3 the earned ending to EVERYTHING.
And that's why STAR TREK: PICARD was my favorite show this year. It wasn't a mere farewell tour that played the easy crowd pleasing hits.... it was an ending, one where each of those gracenotes had a purpose in the narrative and MATTERED.