As it stands right now the only default global chat channel is LookingForGroup, which obviously attracts a lot of boosters and in general people that want to use the channel for things outside of creating groups for Dungeons and Raids.
Blizzard took a few measures against this by announcing a change for Wrath Classic where boosting is not possible any more, and people are only able to post in LookingForGroup if they have a group listed in the LFG/LFM tool.
Players are themselves trying to create a custom global chat channel that allows things outside of the restrictive LookingForGroup, but sadly it’s prone to abuse due to how custom channels work. If the moderator permissions fall into the wrong hands people can ban players and set a password to the channel.
I would propose to just make World chat a global chat, that doesn’t have any restrictions on what is allowed to be posted (apart from anything that breaks ToS and general guidelines ofc). This would also cut down on people utilizing LookingForGroup in unintended ways.