These are my half-assed suggestions for altering the arrangements of the planes to make more sense:
- The ethereal is the plane of souls, the Astral the plane of thoughts and dreams, and both intersect with the outer planes and material. Souls travel from the Outer Planes come through the deep Ethereal, gaining materiality from the elemental planes, and then cross back over at the moment of death. Some get stuck: ghosts! Belief flows through the Etheral, hence why gods end up in the Astral when they die.
- the Astral is where thoughts, ideas and dreams flow to the Prime. When a god does, they become untethered from their source of belief, anchoring in the Astral. Dreams inhabit the Astral.
- The Prime Material is a plane in balance between the Ethereal, Astral, and Elemental Planes. The First World or Feywild drifted too close to the Astral and Positive Plane, making it very story-based and vibrant but soulless, the Shadow Plane lies too close to the Negative Plane, and Ravenloft is more deeply enmeshed in the Ethereal, near the Shadow Plane.
- Illithids come from an early are cut off from the Astral plane.