Things are being done but too softly at it. They're giving them chances to come back to prove that their behaviors have improved, and only issue perma bans if they aren't changing their attitudes. However, doing so is giving these toxic players opportunities to make 4 players suffer for every extra game they get to play, and it'd cause tremendous amount of players to suffer before they're finally removed from the community (which they may return via new account).
While toxic players will always exist, they really should be more strict with punishments and issue out perma ban on first offense in order to cleanse this community, since there's no way community will improve its behavior by itself.