Valve have released an update for Dota 2, which is focused on adjusting the matchmaking system. The update reintroduces the non-role queue, removes the fast/long queue system, as well as adds a fixed amount of MMR received/lost after a match.
From now on there are two options for ranked play – Ranked Classic, where you queue without selecting a role, and Ranked Roles which utilizes a Role Queue games system:
Besides that, the amount of MMR received/lost after a game is now fixed. When playing solo, you will now receive or lose is 30, while group matches will affect your MMR by 20.
Valve introduced role-based matchmaking for everyone in August 2018, previously it was available for Dota Plus subscribers only. Since then the developers have been actively experimenting with the matchmaking system.