He’s too old to be relatable, too young to be a seemingly eternal fixture like Elizabeth was, the Diana stuff made him seem like a cunt, outside that, he’s weird, disconnected, and unlikeable, he’s got weird notions about things like homeopathy… Basically, he’s most of the worst elements of the aristocracy rolled together in an environment where living standards for the average Briton are rapidly and visibly backsliding.
William is younger, more relatable, and less outwardly elitist - he’d be far more popular.