"Snk is not about ships".
You're right, it's not. Its actually about the concept of love. At its core snk is about how love is the 'root of the issue' that Isayama is exploring. Every pivotal moment that has happened in the story; has been based on love.

Ymir's sacrifice, Grisha's decision to quit his mission, Levi's choice to let Erwin die, Hange's sacrifice, Gabi's decision to quit her revenge, Colt's refusal to let Falco go in his final moments..I could go on.

It doesn't matter the form, but love is the basis of this story.

And now that we have reached the endgame, is it really surprising to see love being established?

Armin and Annie become canon. No, it's not forced. Annie literally ended up in the crystal bc she refused to kill Armin. Their bond has been developed since the beginning.

Now, there's another bond which has been there since the beginning and is repeatedly highlighted in the final arc. Hmm, who could it be?

The story is snk started with Eren and Mikasa and it will end with them. They are the beginning of snk and its end.

The fact that Eremika is consistently highlighted in this final arc is no coincidence. The fact that their relationship, which reached its climax "what am I to you?" Was revealed during the climax of the entire series, is no coincidence.

Eren and Mikasa's rel will reach its apex during the eventual confrontation. Do not be surprised then if it's love that saves Eren. Yams is a realist but he's no nihilist.

After all, his essence of his story is that 'the world is cruel, but it's also beautiful'.