I don't mind the "brushing teeth" excuse. Connie has never been a smart character, so coming up with an excuse like that is totally in line with his character.
I didn't like the pie scene, but seeing people complain about it reminded me of the shenanigans that happened in season 1, like Sasha eating a potato in the training camp. Attack on Titan humour has always had that type of vibe to me. It's what would make me reluctant to recommend it to people who don't watch anime, I think there's some bizarre stuff which we've forgotten through rose-tinted glasses.
Unless they flashback to how all the factions got together, it's definitely pretty weak writing. I can excuse one chance encounter. There are enough chance encounters in history for something like Annie to meet Armin & co in a marketplace to be possible. I guess it would've been nice if we had more of an idea of geography, or even a throwaway line of dialogue saying that's where food is being rationed out in that entire city, so everyone in that city looking for food would funnel through there. Considering that essentially half of the Eldian cities are cut off by a big line of titans walking through the middle, so the entire group (luckily) were stranded on the same side it does also make the chances of meeting up more likely.
I assume Mikasa and Jean were in league when they shared that look when Floch was giving his speech. I also guess on the way back to the city, Armin & co ran into Hange's group, which once again I think people would swallow better if we had a better sense of geography and saw them passing one another as inevitable, not as something forced to make the plot happen.
I'm also assuming Armin was the one to meet up with Mikasa and Jean, and Jean thought of the escape plan (as the episode literally said it was his plan), and I would have liked to have seen some resolution between Mikasa and Armin, since they literally had an argument when they last saw one another. So unless Armin and Mikasa make up next episode, as maybe they hadn't seen each other until the escape, I think that whole argument would've been a bit pointless.
I was honestly expecting Armin and Mikasa to be divided for the rest of the season, to really show the original trio are no more; maybe coming together once more at the very end. I was also expecting Floch to be like the big boss of Eldia they had to defeat before they set their eyes on Eren, although Floch may catch up with them before they get off the island.