Everyone is complaining about match making.
No, just a bunch of people who do not know how matchmaking actually works.
It seems more and more common to see unfair matches.
You wont win any argument with "It seems". Get a representative sample of datas, analyze it, and come back with some nice proof to back up your claims.
So I wonder have Riot talked about this problem yet? Or do they think it's all ok and don't see the problem?
There's no problem, it's all ok.
My theory is since they added flex Q with a separate MMR from soloQ (which is totaly fine), some idiots thinks that "omg i'm bronze and matched with plat", but what they are looking at is the soloQ rank of their opponent, which doesnt make sens.
Matchmaking is explained btw : https://support.riotgames.com/hc/en-us/articles/201752954