Haim wasn't rock?Boomers have not been the target audience of the Grammys for at least 15 years. It's all after the younger what used to be MTV crowd.
There is a reason they don't give out the award for classical recording on the air. Or show any rock acts. They are after Taylor Swift and Beyonce.
Also, given that Lorde and Alabama Shakes have been nominated in rock categories, the definition of rock seems to be changing. Twenty-One Pilots and Chainsmokers are even considered to be rock in some cases.