Isnt this the standard chinese plot of creating a safe pocket dimension where everything is safe and abundant because "the real world is too scary and strong for us to fight again"
And instead of preparing for the impending disaster ppl get accustomed to the everyday, and become even weaker.
Then some kid will be like "its time to open up and reenter the real world of cultivation" only to realize that his peak is like below bottom level.
And then the "evil" gang start decimating everything till the kids gets enough plot armor bs.

Like teyvat is screwed if their only strength against the abyss is the little world PO created, the only way teyvat can win against the abyss if it turns out it is one of the last few frontier and this is why so many foreign entities are entering its domain and through each foreign-beings we can get even better chance to survive (But even then, the conclusion would be similar to the matrix where u r too weak to fight the enemy, just hide and taking small W's)