...This isn't particularly bad but when I think of the amount of effort being put into making this system relevant and valuable through so very many iterations I wonder if that time wouldn't be better spent elsewhere...
I think you may be seriously overestimating how much effort they need to put into changing the MMR system. As I understand it they can switch all sorts of stuff without patching the game. It probably doesn't take long to make adjustments.
Get good, scrub.
I don't especially agree with this but isn't it really at the heart of it all?
If people were winning their matches then we wouldn't see threads like this. Several nights in a row I have been helping low level players from discord and we will win every single match. And some of those matches are in high 50% MMR. We never felt like the challenge was insurmountable, even when we had a random that was even lower level than the other guys.
Even with a T1 Antagonist goin' ham on us.
Now you might say that below 70% MMR is shooting fish in a barrel and I would agree. But, really, what do you get out of such a high MMR? You are just buffing the AI for no reason at all. There are people who already got to 100 MMR and they found it wanting.
So, what exactly is the point? There has to be some type of matchmaking system.
And, because for real this thread is always popping up, fixed difficulties would just make people choose one with the most reward for the least challenge. The game is already designed in that fashion.
I guess it is elitist to think this way but if you can't win the match with the challenge presented to you then isn't the MMR doing its job? You're not supposed to have an easy time the whole way through. You're supposed to lose some matches occasionally and every MMR system will eventually set you up to fail.