Apparently you have never had this feature on your vehicle before. My 2000 BMW 528i has this feature and I like it. Yeah it's not as useful as auto-dimming inner rear-view mirror, but it's a legit useful feature to have.
It's not doing "auto-dimming" like the inner mirror, but it's also different from putting on some tint film. You just have to experience it to know.
I am well aware of the auto dimming side view mirrors. My previous German luxury SUV had them and I loved them. Just surprising that Mazda, who is trying to compete with the features of luxury brands, would not have these inexpensive feature on a car that has all the safety features. Just looking for something to calm down the glare.