The idea that every observer has their own unique universe is not a mainstream concept in physics and is not supported by current scientific understanding. In the framework of the general theory of relativity, the universe is generally considered to be a single entity that follows consistent physical laws.
That being said, within our current understanding of cosmology, dark energy and vacuum energy are proposed to be fundamental components of the universe. Dark energy is a hypothetical form of energy that is thought to be responsible for the observed accelerated expansion of the universe. Vacuum energy, often associated with the cosmological constant, is a type of energy associated with the vacuum of empty space.
If we assume that the concept of multiple universes exists (e.g., in the context of certain models in string theory or inflationary cosmology), it is possible that the properties of each universe could vary, including the presence or absence of dark energy and vacuum energy. However, it is important to note that the existence and nature of these multiple universes is still speculative and not yet firmly established.
In summary, while the idea of individual observers having their own unique universe is not currently supported, in hypothetical scenarios where multiple universes are considered, it is conceivable that some universes could lack dark energy or vacuum energy, depending on the specific properties and laws of those universes.