“King has abandoned spooks and the supernatural for the traditional hard-boiled detective/noir tale”This is not necessarily a bad thing, nor an unreasonable change on King's part. King's first novel, Carrie, was published more than 40 years ago, after all.
By the time King published It, in 1986, there was evidence that he was growing weary of writing novels based on supernatural phenomena. His next book after It, The Tommyknockers, was a turkey.
I haven't read Mr. Mercedes, but I did read his 2013 novel, Joyland. While it has a strong supernatural element, Joyland is first and foremost a murder mystery. And it's pretty good.
Even 11/22/63 is more of a fantasy novel than a horror story. Once again, this doesn't keep it from being entertaining.
Despite a few clunkers, King handles most genres skillfully.
Still, I miss the original Stephen King novels--the ones that depicted epic paranormal battles between good and evil: The Stand, The Shining, Salem's Lot, Pet Sematary, etc.
King's writing was also a lot tauter and page-turningly readable back then--which may partly explain my preference for his earlier work.