As far as I can tell, brain rot encourages no thoughts, head empty enjoyment. It expects and promotes the lowest common denominator thoughts, like a thought stopping cliche but for entertainment instead of propaganda.

There's plenty of mature brain rot and it's only non-productive in the same way most media is. I can see calling it decompression-driven, but more as a form of escapist relaxation, like coloring books or knitting. It's main focus is mininal mental effort, hence the name.

TL;DR: Ye, paper is garbo.