About matchmaking (no rant, a question)

During the last month I noticed a change in quality regarding matchmaking. At first I thinked was because of a golden week or something, but then something made me think about a different cause (I strongly believe that during week end/holydays MM can't handle the casual players). I had a constant good winrate, and at some point dropped to almost 50% . Every game was like head or tail, you had an afker or a troll, or enemy team had. Long story short, some days ago I had a message in game, asking me if I enjoyed LOL in this period. After this, game looks more normal to me. Did RIOT tested a new MM system?
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