The rank limitation system is indeed a dreadful new function.
Even if ranks would mean something. But since ranks dont mean a thing it doesnt make any sense but to annoy people. Cash players are from all ranks not just the high ones. They can be found everywhere. The game isnt about skill so this rank limitation is redundant.
But maybe theres more to it..... I can picture it now a new AP item called "VIP Ticket" just 2000AP for 30 days which lets you join any room regardless of the rank limitation.