I think it's different strokes for different folks but the scariest haunted houses for me are pretty dark and give you a sense of being lost or unable to know which way to go through darkness, flashing lights, smoke, dark corridors, mirrors mazes.. etc.... Also for me is when the houses are quiet for a while building tension and then something loud happens and jumps out at you... I feel like that tension building is paramount for me personally. Based on the above I don't really feel that HHN houses really have the chance to enter that upper tier of "scary" houses because of the conga line, ops workers showing you which way to go, extremely loud and chaotic nature of most of the houses. I still think they do a great job of making the houses extremely atmospheric and look fantastic and they def get some good jump scares in, but they don't ever give me the sense of dread that a less attended, well executed, longer, standalone haunted house will give.
This is kind of why I never really complain about the houses not being "scary" I think they are great for what they are, but just by the nature of the beast they never are going to hit me like other houses which are 20+ minutes long and pulse the line. It's kind of like apples and oranges.