I've been playing MW for ~10 years now, and can say that making MMR visible a few years ago was responsible for a dramatic increase in the average MW game quality, and skill level. For instance, before mmr was made visible, our stack got several accounts to 1850+ without even considering it. After it was made visible, we noticed that games which were once easy stomps actually had some difficulty. It is my opinion that removing visible MMRs will have the opposite effect, and regress the average skill level, making good games even fewer and far between.
Seeing MMR of your allies and enemies