I know it's good to use a ground pour,
Depends. At the end of the day it has to do with signal integrity and current return paths.
A copper pour in an internal layer is an invaluable tool for high speed design - and high speed design these days includes basic MCUs, where a rising edge can be in the few ns order.
Per rule of thumb it helps, or at least does not do harm... but.
Depending on the application, a poorly though through copper pour can even create unwanted current paths that will affect your application in a negative way.
It's simply a tool, neither good, nor bad.
Relevant reading:
https://www.analog.com/en/analog-dialogue/articles/staying-well-grounded.html(there are many other good texts)