A little OT but what kind of darkness would you call The Twilight Zone? It's not outright horror--But it is disturbing. Could it be called psychological darkness, ala Grimm's Fairy Tales?
It's pretty much 'psychological thriller'.
But what was scary or dark back then, isn't as scary and dark now. The standards have changed over time. The new standards are full of 'angsty' teenage age drama, and lots of violence and death...