Why parties have no place in solo ranked matchmaking: the real reason

Today in my 3.3k bracket I got two players who were in a party. Because of their party MMR they were put with the 3 of us solo players. However, one of them was actually 2.2k solo MMR player which is in all hell noticeable, especially when he decided to pick Timber and just stand in the lane doing nothing. That's more than 1000 MMR difference.

Please Volvo, for the love of god, bring back real solo ranked matchmaking. This is just ridiculous and frustrating.