They then add decent open world content to get players out and about again?
There is, it's called world quests, and it gives better loot than quests ever did, but apparently that's not enough. What other open world content are you thinking about that we once had?
Because I too remember the times before various difficulties, and open world content was even more lacking then than it is now.
History has proven random queue systems and sligthly harder content dont really mix in WoW. From the times off the heroic dungeons in Cataclysm (which in my opninion still had the best heroic dungeons, even after they were nerved pretty hard just months after the release), until General Nargrim in Siege. Everytime things got the nerfhammer after data showed people couldnt finish the content. I still have fond memory's of LFR Nazgrim, durumu, Garalon and Galakras.
But still im all for a random queue system for heroic and M+ current content, under 2 conditions: 1. Blizzard pledges to dont nerf current content anymore. Like never. 2. They have to implement a spectator mode so we can see the carnage, would be good fun.