How is Historia not involved in a plot involving Historia? (I'm joking)
We had nothing but the main cast last few chapters so I personally don't get that. It's all important stuff that needs to happen for all the characters to survive the next battles.
There's Eren's intentions, and he's probably the biggest influencer of how this will go down considering he is the one who actually control the power. Zeke can't do anything without him.
Levi's squad doubting him and him potentially not being reliable anymore is a pretty freaking huge deal.
The volunteers are actually just there as another side influence. This chapter made me pretty freaking sure the pregnancy is faked to actually spare Historia and then bet it all on the final battle in 6 months instead.
It was made clear Historia had a choice in this and she wouldn't put any child or person through the stuff she went through. The fact that the characters in the story question it to such extent and we haven't actually seen any thoughts from directly Historia, either is what makes me suspicious. I really get the feeling the pregnancy is a diversion to not sacrifice Historia just yet and they know that Marley will be attacking pretty soon. They straight-up say the pregnancy could kill her, too. I think it's a big ruse to divert attention away from her because if she died of childbirth, the Titan couldn't be passed at all. A story wouldn't put all these possibilities on the table if something wasn't up.
Yelena and the volunteers just want Zeke alive. That's it and a coverstory would have the same effect as the real thing.
With all the different fractions it might seem complicated, but Eren, Zeke and Historia are the center right now. But that's just my perspective of the whole thing.
At the same time, I do think a bunch of time was spent setting up the stuff happening to the main characters. The Marley arc in particular introduced a lot of new characters and personally I did grow to care for them, but I can also understand if people didn't. It's all setup that I think needed to happen. But that doesn't mean everyone is grabbed by it.