I would love if Valve made a rule against these spam guides

Valve doesn't bother when it comes to this sorta thing. If they can't automate it, and it requires a human, they won't do it.
This leads to much worse consequences - the CS2 and DOTA2 communities are toxic cesspools. These games which actively require good communication are filled with the most vile racist sexist everything-phobic people (and kids!) you've ever seen. It's the wild west of the Internet, like 4 Chan. It's been like this for years, and it will continue like this because handling that isn't something they can automate, and hiring people costs money...