After Dota 2 had introduced the new matchmaking features, fans started to have issues with queue times. Devs from Valve tried to explain why the algorithm is causing it and what are the criteria that make two teams meet on the server.
Up until recently matchmaking had a hidden limit of 20 minutes for the queue time, after which the system tried to start the game asap even with a big rank disparity between the participants. This caused many upsets both from lower and higher ranked players who would prefer to play with opponents of their level. This made Valve revamp the system which now will try to create more balanced matches for a price of longer queue times.
However, the devs have yet to figure out what is the most suitable solution. Jeff Hill apologized to those who were upset with longer waiting time, as it is hard for them to please each end every player of a fanbase that big.