I don't think the Haunted House lineup has ever been cohesive; even if you look at a gold standard year like HHN18 they lumped a spaceship, zombies, Jack the Ripper and Fairy Tales together under "phobias". Which is fine though, it's way more important to have variety than cohesion in a lineup, and the facades are so far from the midway the clashing themes don't really matter. They exist in their own separate world.
I think when people say cohesion what they're really looking for is the entire park to feel "full". Consistent music loops that use spookier music, dead spots between scarezones filled with hordes, maybe smaller shows, or even just passive decorations instead of just #HHN34 projected on walls. A lot of this passive atmosphere has disappeared over the years, right now once you make it out of the front of the park the entire lagoon area can feel like one big deadzone.
An icon makes a tie-in easier as they can host the event, but even just a consistent theme like a haunted garden/conservatory can work just fine if they commit to the vibe like they're saying. The return of a chainsaw horde on the spec map is a good sign if it comes true.