Sometimes I think the Horror genre is unfairly burdened by adult audiences demanding 'Scary Films' based on their nostalgia which is silly and aggravating because they're not kids anymore so you can't really recapture that. Well, I suppose you can try by being heavily retro like STRANGER THINGS.
With that said, I do think a mature audience can be taken on a ride with different scares that do not rely on the same old Slasher film tricks or jump scares when that fails.
Well.... not Scares exactly, but walk the audience into new concepts that are disturbing or unnerving or go for the MindFvck(David Lynch, David Cronenberg, Shinya Tsukamoto).
Personally, I consider the best Horror to be very closely tied to Wonder and somewhere in between dealing with The Uknown. This last bit might were difficulty lies as what triggers a sense of Wonder in people is very subjective and it would be difficult to market. Unfortunely, I think those who hold onto their nostalgic ideas of horror are the hardest to get to be open to wonder because they see it as a distraction. They would rather just become Eli Roth gore hounds.
Maybe the movies that do manage to do this are the ones that ultimately become Cult Film favorites regardless of their initial box office success.