They went tiers because it's more "casual friendly," I guess? But even the casual players hate being deranked and the seeming RNG of ranking up in general. I don't think their best and brightest were in charge on that aspect of PvP.

You can have Elo and "tiers," they aren't mutually exclusive. How it's *supposed* to work is that the tiers are just window dressing. Instead of saying "you have 2776 rating," you would tell someone "you are Platinum with 2 stars, and you're almost to your third star!" The rating is what determines matching and their progress through a tier, but what's shown to them is "tiers" because they're fancier and it sounds better to go "congratulations on making it to Diamond status!" than "congratulations on making it to 3082 rating!"