That was an almost perfect end to the season, and the series. Considering much of the beginning of the season made me think Mike & co were out of gas in the writer's room, and this upset the status quo enough to make me really want to see a season 6, mission accomplished. I wonder if, similar to Disco, they were given time to add additional material to help wrap up the series more neatly at the end. Because this works as a hopeful conclusion, setting up the possibility of further adventures or a spin-off series.
The first kudos have to do with weaving together almost the entirety of Season 5 by the end. It's not a surprise it's a direct follow-up to the previous episode, and that the rift plot is dealt with. We also knew from advance photos that Ma'ah and his brother were going to be here. But they also worked in Ensign Olly and Starbase 80, meaning over half the season at least related tangentially to the finale. I think making the series closer focus on the ship's crew and some recurring characters was the right call, rather than adding more gratuitous legacy Trek cameos (though we do see the Anaximander's crew made it through to this reality by the end).
I like that compared to the previous episode, the effects of the different realities were more muted here. Having the one Klingon vessel shift into a Disco-era one was a nice Easter egg for those who insist it's not canon. Otherwise we mostly just get a tour of different Starfleet-class ships.
The humor is very subdued here, as befits the high stakes of the episode and high level of action. Honestly this is a pretty classic Trek format which could have been on TNG with only a few tweaks.
But the episode is not perfect. First, the sister of the Klingon brothers that Ma'ah killed is an idiot. Admittedly, she's a secondary antagonist here - the anomaly is the real issue - so I don't ding the episode much for this. The shoehorned mini-arcs for Tendi and Rutherford, though, I think were pretty bad. Tendi's conflict with T'Lyn was telegraphed earlier in the season (Fully Dilated), but it was presented as resolved there, so it comes out of left field here. Not as much as Rutherford, who starts the episode suddenly veering into angry for no reason, then resolves a huge, heretofore unknown, personal conflict by the episode's end. I love where he ended up, but they treated him as a non-entity through the entirety of the season. One wonders if they planned for him to have this arc for Season 6, and then had to speedrun it here so they did something with him.
Boimler works out much, much better, having resolved his silly "PADD arc" through the course of the episode. Mariner didn't really have that much of an arc this season, but seeing her (largely) act as the voice of reason here is refreshing, and shows how much she grew over the course of the season.
We end on an intriguing note, with the status quo upset in many ways. Freeman is off the ship, with Ransom now captain. Mariner and Boimler are both "provisional first officers" - leading to potential conflict. Rutherford has removed his implant and seems to be finally coming to terms with his romantic feelings for Tendi. Starbase 80 and the Anaximander are right there in case they want to do an animated show covering alternate realities instead. There's so many new story possibilities. I wish the show had felt comfortable upsetting the status quo earlier, because something similar would have made Season 5 as a whole much, much more enjoyable. Instead we got mostly mediocrity, with the season only really finding itself in the back half.