Tumblr has only always cared about shipping and not given a single fuck as to the 'real' plot of the manga.
Why can't Isayama go a single chapter without creating new plot holes? Is it really that hard to just think things through for two seconds?
First of all, there is no goddamn reason for Ymir to serve Eldia once she bonded with the tree. Yes she was a slave but it wasn't like she was raised from birth to be one. She was captured when Eldia raided her village, and judging from her apperence, it couldn't have been more then two years ago. I know someone will try to explain it away but her just being that nice, but serving Eldia means slaughtering thousands of people. If she wants to be nice everyone, she would, you know, not kill them just to please someone who treated her like shit.
Second, why did Friedia say that Ymir was a good person that everyone should strive to be? Before this chapter came out, I assumed this meant that Ymir was innocent, it was just her descendents that did all the stuff King Kuck decided every single Eldian has to die from. But we now we know that Ymir willingly participated in Eldia's conquest, so why does King Kuck like her? If the idea is that he views her as what all Eldians should be like, a complete slave who obeys without question, that would really work, it would make sense and suit his character, but the way the narrative tries to portray the king as pitiful makes it clear that's not the intention.
Third, if multiple people eating the same shifter splits the power evenly between them, then why the fuck are there only nine shifters? Both Eldia and Marley would have to realize there's an advantage to having more then just nine shifters. Hell, Marley was stretched thin when they started their first invasion of Paradis and they could only send Reiner, Bertholdt, Annie, and Marcel in alone without Zeke, who was the leader of the team. If they could just make more shifters, why not just do that? You can't say they didn't want to risk the power getting weaker, Ymir's Titan was split nine fucking times and each one, except the Cart and Jaw, is incredibly powerful.
Fourth, Isayama still can't world build worth shit. The Eldia chieftain refered to Marley as the "cursed Marlians", so there was already hatred between the two of them,, so what the fuck was that all about?
Fifth, what was the point of having Kruger say there is no truth in this world, and that anyone could be made a God or a Devil depending on how history paints them, if you're just going to show the truth anyways?
Sixth and most importantly, with the Rumbling now finally activated and the entire cast sent on a one way trip to the ending, it's finally confirmed that putting Annie in the crystal was completely and utterly pointless. There was zero reason, from the perspective of the audience or the characters, for Eren to not just eat her at the end of their second fight. Its not like it would've Instantly given him all her memories, it's been established that blood relation plays a big role in how quickly one gains their victim's memories.
But there is one thing I really like about this chapter, and that's Eren managing to free Ymir from being a slave by simply treating her with compassion, hugging her and telling her that's she's better then she thinks she is. Not only is it brilliant that the way to free her was to simply tell her that she deserves to be free, but it's finally the old Eren returning. Until he returned to Paradis, Eren has always been telling people to believe in themselves, and that they don't have to just accept the status quo and remains slaves.
Only here, he's not saying it in a passionate youth way, he's saying it in a much more wise, mentor way. It's a perfect evolution of his character, one we haven't seen since his talk with Reiner, and I hope that Isayama will switch him back to the Big Boss personality he had in Marley, and not change his post time skip personality for the fourth fucking time.
I mean, that's the only good thing about this chapter is Ymir and Eren. Everything else is lol. The whole thing is trying to force shit to fit that doesn't much make sense. The only thing I think foreshadowed was time travel fuckery. Problem is, he never ever fleshed it out, so it was constantly shifted, changed and altered. You can't do a time travel story without establishing rules.
I'll try to answer your points:
1) Isayama hasn't fleshed out Ymir and wants to contrast her with Eren as her being a 'slave' and Eren freeing her. As in, somehow the Attack Titan is the
AMERICA freedom Titan and King Cuck restricted its power to make Ymir an eternal slave. Note: This is not explicitly stated, implied or thought out. There's no evidence at all for this and requires assumptions to make true.
2) No idea. Its a complete mystery.
3) Isayama did not know where he was going with this. He is barreling towards the end with no fucks given. He has had no idea how his world works and arbitrarily changes it based on the plot requirements and to jam it in there. There is no explanation for this. The walls being named after the daughters is hilarious and pointless at the same time.
4) Nobody knows. This should have been established a long time ago. He's forced to rush the world building because he's left it in the dark for so long.
5) Isayama wanted to make the story look deeper than it is.
6) Isayama did not know where he was going and left her in the crystal for years and years. It turns out in the end, it was utterly irrelevant. He does this quite a lot. He sets up something to be important and just drops it. Historia's pregnancy, Levi and Hange, Annie in the Crystal....all left hanging. They might be rushed and crushed together to just have some resolution but it probably won't be satisfying.
And who knows what the fuck he's going to do. He just changes plot, personalities and everything he needs to to make things fit. It turns out, shocker, that Eren was going to do the rumbling all along, which everyone knew. Yet he kept it hidden like it was this massive surprise. Another waste of the reader's time. Its not 'hurting' the reader if you bore them and do the expected thing.
The sad thing is, if we knew Eren's goals, Ymir's history beforehand, it could have been a real emotional moment. You could have spent the entire chapter with Eren and Ymir discussing things and make Eren look like less of an asshole, trying to free this young girl from being a pawn for eternity. The problem is that these should have been the central themes all along, yet there was no planning to this. They're just crushed in at the very end. That Eren's goal was this over-arching one, to prevent this young girl who never wanted this power to be a plaything for the nation's of the world. To end Titans, to eliminate them, to free Ymir from slavery. Which makes Eren's freedom boner make sense, meaning he was the only one dedicated enough to do it. No time travel fuckery, no "ALL ACCORDING TO PLAN", just a desperate cry for help from an enslaved young girl and Eren's will for freedom.
It'd be so thematically poignant, this human drive to freedom. That tough decisions and friendships had to be sacrificed to free the world of the titans and Ymir from her living hell. Its just another massive disappointment from this manga. There's SO MUCH wasted potential here. We're just getting crappy cliff hanger after crappy cliff hanger. I honestly can't be bothered to even have a hate boner for this much anymore.
All in all, this chapter just makes me sad. The potential was there, even with the shitty Game of Thrones stuff. Make Eren Big Boss, driven by pure will. Make his motives known. Make Ymir's history known. Imply that they're eventually going to meet with Zeke, who wants to keep Ymir enslaved. Build this up, ratchet up the tension, make this the ultimate confrontation of the manga. Freedom vs. Slavery. Status-quo vs. a New World. The End of Titans or the Beginning of a New Cycle. Instead, he just constantly went with 'SHOCKING REVEAL', like it was a daytime soap opera.
Instead, its just pointless reveals that degrade the quality and themes. You can see there was a chance for something good here. Isayama is just too autistic and terrible of a story-teller to do it.