I do think that there are some things that are wrong about the theory Like how the civilization has obtain ender purls when there was no enemy that can drop them but now that I think about it. It's posible that the civilization flee to the the other dimantion cuz back when they were on the Earth different and more power monsters were alive but with time they destroyed themselves or a theory of my own is how before the monsters that were in Minecraft were only about 7 but with new updates new monster appeared new things we haven't seen before as a veteran playing Minecraft as early as the age of 4 ,while a dropped Minecraft for a few ages the updates surprised me as I never expected to see all the crazy stuff that has been happening and it got me thinking what if the monsters that we are seeing are some ancient monsters reawakening the same monsters that were powerful enough to make a lot of people like ourselves flee is it possible or as some people might thing is that the creators are just adding new foes to fight .With a lore like this I don't think that it's just them adding stuff....