You know guys, recently re-read the chapter and I think you guys have it wrong.
Before dropping this statement Eren clearly says "I don't really know, but I think _______". Think is the keyword here. He doesn't know.
Shortly after his death, however, Mikasa meets Ymir, and in that scene, we see a vision of Ymir hugging her kids over a dead Fritz. Which made me think that perhaps her reason for keeping up with this slavery was not loved for Fritz but love for her kids, and the subsequent Eldian.
Every founding titan until Eren was her distant grandchild, and I think like Eren, she just couldn't let Indians die out, no matter how better it is for the world, but being a slave she couldn't really work on improving Eldian lives either, that is, until Eren freed her.
That's my two cents, and I think it makes a lot more sense and (maybe) what Yams was going for.
All this is not equal to "I love the ending". I don't.