The real irony here is that Retail sees far less use of the Dungeon Finder than Classic would. Mythic and Mythic Keystone dungeons don’t use the Dungeon Finder and automatic group creation, they use the Premade Group Finder. So really, the only people using the Dungeon Finder are people levelling, people doing dungeons to finish quests, or people gearing up a little at the very start of an expansion. Otherwise everyone is doing dungeons the old-fashioned way, even having to travel to the instance entrance in the world.
I think it would be difficult for even the more ardent Classic purist to be upset over a Premade Group Finder compromise. It allows you to advertise a PUG to your local server community without needing to spam Trade chat. What would the counter-argument possibly be? Yeah, it didn’t exist during Wrath, but LFD did so… are you an originalist or no?
To be honest, I completely forgot about the Premade Group Finder because A) I’m not playing WoW and B) I had less than zero interest in Mythic dungeons when I was playing. I would still prefer an LFD system overall for less serious content though, especially for those on smaller servers. Sometimes you just want to press a button and get group content. If it’s good enough for PvP, why not PvE?