I think a year ago they tried to fix the rating system, but they messed up. From that moment the number of smurfs really went up. People are pushing main accounts by playing with 3 smurf accounts just to get easier enemies. It is a really bad experience.
I made this thread about the rating system. One of the suggestions is changing the matching. Nowadays you are matched based on average rating where every players has equal weight. So if a 5000 player is playing with 3 other players of 333 elo, then the total is 6000 (rounded) and on average it is 1500. So they are matched against another team of 1500 average.
One of the solutions is to change this calculation to put more weight on the higher rated player. As result this team will be considerd as 4000 elo on average and be matched accordingly and will be matched against another team of 4000 elo on average. This will already limited the impact of these smurf accounts.
Have a look at the thread i posted above for the full discussion about this subject.