The omniscient point of view, which gives the writer license to go into any head and no head at all and to speak as a God-like observer, or even to address the reader directly, had its golden era in the 19th century.
Modern readers and writers prefer the more intimate view of first person or limited third. Both are much more natural. After all, we live confined to one consciousness, one point of view.
Omniscient creates an often chilly distance between the reader and the story; it provides the broader vistas seen from a mountaintop as opposed to what can be observed when studying an object in your hand.
But what did that 19th century novelist, and those who buck the trend and use the omniscient point of view today have that the modern intimate writer lacks?
The ability to get in backstory and exposition in a way that is natural and unobtrusive.
First person narration has to practically stand on its head to do the same. First person often disguises needed information as dialogue, but that only goes so far. A character who says, “You and I grew up in New Jersey.” is stating what the other character clearly knows. It is only in there to inform the reader.
The first-person narrative can divert briefly into a bit of backstory or exposition, but it always takes the reader out of the “now” of the story and weakens the sense that the reader is listening to the voice of the narrator.
If you have any doubt that this is true, notice how hard it is to transition back into the “now” of your story and regain the sense that the story is being told by an individual “I.”
Here is a example of the ease with which a broad description can be written, unencumbered by the need to justify its presence by having someone observe the scene or talk about it. This is the view from the mountaintop that is so easy to achieve when writing in the omniscient point of view.
“Every day at the same time the schoolmaster in a black skull-cap opened the shutters of his house, and the rural policeman, wearing his sabre over his blouse, passed by. Night and morning the post-horses, three by three, crossed the street to water at the pond. From time to time the bell of a public-house door rang, and when it was windy one could hear the little brass basins that served as a sign for the hairdresser’s shop creaking on their two rods.”
From Gustave Flaubert’s “Madame Bovary” published in 1857.