It manipulates the picture to give an unnatural enhancement to the parts of the picture that are in focus. It gives an uncanny quality to whatever is on the screen, distorting the carefully refined work of cinematographers, editors, etc. and makes everything look like a soap opera.

Some people defend it as a good enhancement for sports (I don’t agree) or especially video games (I have never owned anything fancier than a Nintendo Switch) but for the most part it makes most TV and movies look wayyyyyy worse, in ways that don’t make sense outside of an electronics store showroom.