While skeptics can of course say they are liars or confused or their mind played tricks or under the influence of brain chemicals (like drug induced states), these people express absolute certainty about their experiences. There are too many to ignore or to try and discount as somehow deluded.
No, it doesn't need to be taken any more "seriously" than my nephew's hallucinations.
My nephew is a classic schizophrenic, including the paranoid delusions. He doesn't take drugs to get him to this state, his body provides all the organic functions it needs to do it. He lives with this every day.
The "people" or "entities" that he "sees" and the voices that he hears, in fact the entire conversations that he has, ARE MORE REAL TO HIM THAN ACTUAL PHYSICAL REALITY. He can TOUCH me and know I'm "real," but when he sees visions -- to HIM -- they are more "real" than I am.
When people are in such a physical state where their bodies are creating these "visions" and "images" and sights and sounds, I can very much believe they are VERY REAL to them at that time. Their bodies and therefore the organic chemicals and compounds acting on the brain are very likely much like in those moments very much like what my nephew has to deal with on a daily basis.
He isn't lying. He isn't making things up. He has organic things going on, which is why he MUST take certain medications to keep that under control.
The sort of delusions he has is greatly different from the delusions that, say, theists have regarding an imaginary realm with god-beings.
It's organic, just like the types of delusions that people who experience NDEs have.
If we can get ANY benefit from "studying" those it should be in terms of the chemical reactions going on in the brain in hopes to find even better, more efficient drugs to help people like my nephew, NOT to try to shoe-horn in some imaginary god-being realm.