Anecdotal evidence in the spoiler below, but anyone who has been playing in the solo queue these past few days or keeping an eye on the forum know what I'm talking about already.
Just got out of a match with my just-for-fun gauss rifle Shadowcat. Even with only 25 rounds of ammunition, I got the top score. I wasn't even playing very well, I was almost standing still in open terrain, just shooting at people who were new to the game and didn't know how to control their mech.
Anyone who has played with me or have checked my stats know that I'm not a particularly good player, even for Tier 2.
I know it's an established fact that a lot of "weekend warriors" arep laying during holidays and such, but that doesn't explain why MM has just given up.