"brainrot" is not used that way

https://www.urbandictionary.com/define.php?term=brainrot

The best definition I see is

> the crippling addiction to low effort content

But also have seen it used plenty to refer to the low effort content itself

Brainrot is a small portion of social media

I have seen it used plenty by younger people even in a positive sense as a genre label for the aesthetics and humor of their generation.