Jeremy Crawford says, "It is a realm of thought which connects to all of the Outer Planes, which are places ultimately of belief. And so if you are in this realm of thought, you might be there physically but you are in a way starting to bleed into almost a 'thought version' of yourself. This is one of the reasons why creatures don't age in the Astral Plane."
Not too far off from what Yaarel has been saying! I am digging what they are doing to make the Astral Plane weird and very different from anything else. I'm getting shades of "meddling in things you don't understand" in the way spelljammers use the Astral Sea as hyperspace to travel between distant stars. I'm thinking that even hardened Wildspace sailors probably go pale and maybe even have a panic attack the first time they enter the Astral Sea.
In my view, it is more consistent, and makes more sense, when:
The astral plane and its dominions and wildspaces are strictly a mindscape of information constructs. Virtual realities of consciousnesses.
By contrast, the ethereal plane and its domains, fey and shadow, are spirit realms of actual physical forces that exist within spacetime. These ethereal forces, including fey and shadow, can interact with the material plane.
The ether is where desire, will, and dreams, reshape physical realities.
It is worth distinguishing the "dream" of the aster as strictly a collective mindscape, from the "dream" of the feywild that is a twilight zone where the dream becomes an actual reality with tangible force.