The scroll hijacking is by far the most annoying UI trend. Its only use should be for presentational slide deck type websites. And you better be sure you’re providing a grand experience that’s worth it.
Even more pointless are the websites where the scroll hijacking tries to mimic the natural scroll momentum. You can just tell it’s off and I usually leave any website where the scrolling feels wonky.
A few poorly thought out wordpress themes are probably to blame for making this more popular than it should be. I doubt many developers and designers would choose to waste their time implementing something so useless otherwise.