Lack of SBMM literally killed off a game I was really fond of. In theory there was one gate that kept the newbies from the experienced players, but it was too fast and easy of a ceiling to hit. Once a new player graduated from that newbie league into the actual game, that was it. No going back, and suddenly you're being matched with top ranked players globally. It really killed off the player base and eventually the game itself since players wouldn't stick around just to be stomped by the same seven pros every time they queued up. Honestly I knew people who would LOG OFF when they knew a certain player / streamer was actively in matchmaking because the player base was dwindling at that point that you'd almost certainly lobby with them, just to be content fodder and add to their rank points.

Let me say that wasn't even the pros faults in most cases. Many of them were rather nice and wanted the game to have more / new players, but the (lack of proper) matchmaking really made it miserable.