I think you're both ignoring the possibility that it's just that there aren't enough plat+ people to support constant play.
I think the current set-up does well for its purpose - people can farm their way up to plat via the ranked rooms and then they can use the matchmaking function. Maybe we can consider a gold - plat and a plat - gold room, but that also might be something people prefer to set up next season, if at all.
Either way I can bring up the discussion