"the matchmaking graph at the start of the match is a terrible idea."
Agree, and disagree. Yes, it's a bad idea in the sense that it causes people to mentally check out of the match even if they don't actually quit. I've done both. A lot.
But I also think it's pretty brave on their part to show us up front just how terrible their population and matchmaking problems are at the moment. As others have said, a few seasons ago they were trying to up their skill buckets from five to "more than five," but I'm pretty sure that now we're down to three. Two at off-peak. That's just sad. And the thing is, I know what I'm getting myself into with every match, and I knew it long before they so generously illustrated it for me with the graph. But there are so many people in this game that either don't see the graph, don't understand what it's telling them, or just plain don't care or don't believe it. I'm not saying that all the data on the graph is 100% accurate, but it's still a pretty good indicator of how you can expect the match to go. And that's always how it goes.
All in all, I'd rather have the graph than not. Yes, I can see the storm clouds on the horizon for myself, but I still like to have a weather forecast just to confirm that I'm not going crazy.