I'm in the "Sun & Moon's pokedex descriptions are par for the course" camp. I remember hearing the Pokedex entry for Drifloon back in Diamond/Pearl, about how sometimes children mistake it for a balloon and get kidnapped as a result. And that was originally written ten years ago!
It's just there are like, 900 Pokemon now. That's a lot of room to write some pretty creepy descriptions. Sort of like how we have nearly 60 Legendary Pokemon as of Sun & Moon. You have five or six creepy Pokemon per game, and that really begins to add up over time.
Here's more, from previous Pokemon games:
Misdreavus (Emerald)
"A Misdreavus frightens people with a creepy, sobbing cry. It apparently uses its red spheres to absorb the fear of foes as its nutrition."
Shuppet (Black & White 2)
"It feeds on the dark emotions of sadness and hatred, which make it grow steadily stronger."
Duskull
"It loves the crying of children. It startles bad kids by passing through walls and making them cry. " (Platinum)
"It doggedly pursues its prey wherever it goes. However, the chase is abandoned at sunrise. " (Diamond/Pearl)
"If it finds bad children who won't listen to their parents, it will spirit them away--or so it's said. " (HGSS)
Haunter
"In total darkness, where nothing is visible, Haunter lurks, silently stalking its next victim. " (Gold)
"Its tongue is made of gas. If licked, its victim starts shaking constantly until death eventually comes." (Silver)
"It hides in the dark, planning to take the life of the next living thing that wanders close by. " (Crystal)
Gengar (Fire Red)
"It is said to emerge from darkness to steal the lives of those who become lost in mountains. "
Lampent
"This ominous Pokémon is feared. Through cities it wanders, searching for the spirits of the fallen." (Black)
"It arrives near the moment of death and steals spirit from the body." (White)
"The spirits it absorbs fuel its baleful fire. It hangs around hospitals waiting for people to pass on. " (Black & White 2)
Gourgeist (Pokemon Y)
"It enwraps its prey in its hairlike arms. It sings joyfully as it observes the suffering of its prey."
Marowak (Crystal)
"Somewhere in the world is a cemetery just for Marowak. It gets its bones from those graves."
Shedinja (Ruby)
"Shedinja's hard body doesn't move - not even a twitch. In fact, its body appears to be merely a hollow shell. It is believed that this Pokémon will steal the spirit of anyone peering into its hollow body from its back."