Point is he is criticizing Google but still collecting checks from them. That's hypocritical. He would have a little sympathy if he never worked for them. He had decades to resign. He didn't. He stayed there until retirement. He's even using gmail in that post.
I still don't see the problem. You can criticize things you're part of. Probably being part of something is what informs a person enough, and makes it matter enough to them, to criticize in the first place.
It is OK to collect checks from organization you are criticising. Getting money from someome does not imply you must only praise them.
Rob Pike retired from Google in 2021.