I personally don"t think playing free rolls will get you better at mtts regardless of how bad the players are.
I think starting at the micros, studying and doing hand reviews will actually improve you MTT a lot more than seeing tons of mistakes and gambles we see in free rolls. Even at micros, where the investment is small, sure you do get tons of bad players to see what are bad plays. However, they are no where near as crazy as they have some money on the line and I think you see by far enough mistakes in the micros to improve your game whilst also getting a better feeling for mtts in general.
I think free rolls in general are a terrible place to learn, unless they are private free rolls, other than that they are a waste of time and you learn nothing.