Just to put this out there, the non-IP attractions are built on very popular tropes like a haunted houses and a pirate adventure are arguably IP-lite. You don't have to explain to someone what a Haunted House is. They are timeless because they are very good haunted houses.
The question is, out of the millions of people coming to WDW every year, what does a non-IP attraction get you that an IP attraction can't give you? You can give a personal opinion, but you really need to thinking of large amounts of people and not individually.