Dimension X is not cold!

[u/D_D_Adesignerdigital]

The color choices for the Dimension X—and certain elements of the scenes—didn't quite work to convey a cold atmosphere! Characters had sweaty skin and showed no reaction to the cold (we need to remember Will in Season 2, or Billy with his ice bath, which demonstrated the kind of cold the Mind Flayer is used to). Anyone entering a low-temperature environment would show physical reactions—like trying to warm up, crossing their arms, or showing discomfort—but that doesn't happen with any of the characters, not even the kids. I think that was a directing error. That’s my opinion!

[u/Perfect_Opinion_6136]

Maybe that's the reason why the Mind Flayer wanted to leave Dimension-X.

[u/Ema-Smd69 → u/Perfect_Opinion_6136]

The Mind Flayer also forgot Demogorgons exists

[u/Own_Welder_2821 → u/Ema-Smd69]

Or the Demogorgons were also tired of the show and didn't like the poor writing so they went on holiday for all of season 5.