Board Thread:Manga/@comment-34196931-20190808205129/@comment-33179669-20190812162826

From the stuff above, it sounds like the control over the almost non-sentient (but mostly certainly sapient) Ymir is a balance of power. Royals can access Ymir, but can't control her. Theoretically, average Subjects can control Ymir, but can't reach her. Eren and Zeke then completely and utterly broke the rules to the Paths, thus being the reason as to why we can't have nice things anymore.

Or something like that.