I put this thread into the Lounge because in some ways it is a fairly 'sensitive' area, as if people disclose dream experiences it may be a bit private, rather than simply rigorous arguments. The nature of dreams is so complex and, as you say, it hard to know what a 'proper lucid dream' is. I do remember reading some time ago that flying dreams are meant to signify 'upper states of consciousness.' I think that the closest I come to having actual flying dreams is some borderline sleep experiences in which I am floating around my room. However, these have not been particularly pleasant experiences.
Jung was probably correct in indicating that in the interpretation of dreams the individual meanings of the dreamer need to be taken into account rather than rules of interpretation being applied universally. He also looks at dreams in connection with the understanding of symbolism. It may be that dreams, including lucid ones, are about connecting with a different angle. Huston Smith, in 'Forgotten Truth', speaks of symbolism being about being able to explore different 'levels' or 'dimensions of reality'. Also, Peake refers to 'inner space' as a reality in itself.
It may be that there are two opposing approaches to lucid dreams or 'unusual' dream states. One is that which is extremely dismissive. In addition, many people are inclined to the view that exploration of symbolic levels is pointless. In contrast, some people interpret the symbolic experiences in a concrete way. Even if imagery and other aspects of experiences occur with eyes shut, on the borderline of sleep, if people read too much into them it can be dangerous. That may be the way in which many end up going into the territory of 'psychosis'. I consider myself as fortunate that I discovered Jung's writings during adolescence, because I think that otherwise I may have gone on to develop psychotic illness. It is such a fine line, because I have worked in mental health care and seen people struggling in how they understand and interpret symbolic experiences.
There are various models of understanding the various aspects of lucid dreaming and associated experiences, including the shamanic viewpoint. That is interesting in the way in which it refers to voyages to upper and lower worlds. I find reading literature on shamanism, including the work of Mircea Eliade, very useful. Also, there is a lot of interesting writing within Eastern literature, including the model of the chakra system One other important idea is that of 'kundalini', as the energy force rising from the base of the spine to the centre of the forehead, spoken of by Gopi Krishna. He speaks of all kinds of imbalances which may occur in the awakening of the 'kundalini serpent', and how it can lead to 'madness'.
The whole phenomena of lucid dreaming and 'astral travel or projection' is one which may be fraught with dangers. I can understand why many choose to leave it alone completely. Some find it extremely important though. I fall into the category of those who choose to explore it. The main issue may be about keeping balance and it is not easy. I definitely have experienced times when I have lost that balance. Ideally, it may be best to have some kind of mentor but they are difficult to find, and there are so many charlatans. Careful reading from various viewpoints may be the best, with a basis in philosophy or critical thinking may be the best approach, and some kind of grounding in the physical world.