There is such a system in place actually [0]. It is believed that the playerbase is separated into pools [1] somewhat based of this number. How it is calculated is anyone's guess.
Then it's not working. There are console commands that will print your toxicity metric. I routinely score ~9800 out of 10,000, i.e. friendly, and several times a week am matched with very toxic players.
Are you on the extreme ends of mmr? I have a high rating and rarely get people that don't get along. On the other hand, with the introduction of international ranked, maybe they shelved this for a consolidated pool.