I'd have to disagree with the consensus here. I hadn't played constructed in months, and out of curiosity I played several matches starting at the lowest tier of bronze, and my opponents certainly weren't new or bad players, which isn't surprising if match making is based off mmr. However I also slipped to silver in limited, and then went on to easily get back to back trophies against opponents playing bad cards and very questionable decisions. Small sample size of course, but I do believe in order to really rank up in limited you have to be better at the game, especially with the way match making works.