This whole plan is just one huge **** up. Really.
I mean, the plan can work only if the people look at the moon, right? So what if the moon is blocked by clouds? What if someone goes to sleep when the sun is still up and doesn't see the moon, and then wakes up to see a bunch of people drooling because they were caught in the genjutsu? What happens during the day, when the Moon ISN'T there or when the moon CAN'T be seen in the night sky?
Aside from the fact that the whole thing is completely insane, what the hell happens when Obito, the caster of the Jutsu, dies? The people would break out of the genjutsu and continue living, right?
No.
In Tsukiyomi, 1 second is the equivalent of nearly three days. This would that within a day of being caught in the genjutsu, most people, in Tsukiyomi would die from "old age" in the genjutsu even though they're still young in the reality.
And in the reality, how would their bodies get nutrients if they're in a genjutsu world? They wouldn't be able to because they can't move and because they think they're "eating" in the Genjutsu world. which would mean that all the humans would die within a day or so.
So either Obito wants to kill humanity, or Kishimoto just screwed up as he usually does.
I'm going with the latter.
But that still wouldn't explain how the Genjutsu would work when the moon is hidden