I have finally understood something today. I didn't understand why people seemed to be spending so much time in the astral plane. It's a higher plane than the physical, but only the surface of what's after (the mental plane).
Teachers say one should not spend too much time in this plane, as many lower beings are there.
So, for indigo / crystal people that meditate and expect to raise their consciousness to the astral plane, that's nonsense! They are probably already beyond it.
Or if indigo / crystal have people trying to attract them to the astral plane (thinking they will raise their consciousness), they are actually lowering their consciousness.
Functioning in the mental plane is actually working with images in the mind, not with language or emotions. This is something which is usually observed with people in the autism spectrum, or people having a strong visual mind (creators, architects, engineers ...) : they directly work with this intuitive mind.
I hope it helps! (and happy to refine anything with you, I'm not an expert in that topic)
https://en.wikipedia.org/wiki/Plane_(esotericism)