Flex queue is a troll's wet dream.

Remember the days when people intentionally tanked accounts to bronze 5 just to experience chaos and fuel the fire that is bronze 5 mega ELO heaven/hell/Ragnarok?

well boys, the answer has been given to them in the form of flex queue where you can goof off like a mad man without consequences to your actual MMR,

The MMR that matters; ranked solo.