Personally, I believe that the distinction between "unnecessary detail" and "the point" is mostly subjective and in the mind of the reader.

The point of a book is to get the reader to reach a certain understanding. Every brain is different and while one literary path might get some readers to that destination, other paths may be required for others. But there is no singular point of understanding that exists solely at the end of that path. The path itself is what builds that understanding.

Part of the art of writing is covering a large enough space of multiple paths to get most readers there without too many of them getting lost.