Theorizing about the nature of consciousness without having been subjected to it's multitude of altered states is an obvious waste of time. If you can't or won't venture into the "field", then at least have the humility to address the aggregate experiential data of those who have.
The trouble is that the sort of drug-induced insight (or pseudo-insight as some would call it) you refer to is usually accompanied by strong euphoric effects, which impairs your ability to dryly reason about those experiences even a long time after the fact. Nor can I completely shake the impression that those who believe a e.g. a DMT trip offers genuine insight into the nature of consciousness simply had an insufficient grasp of the subject beforehand.
There are altered states of consciousness that occur naturally and don't lead to a sense of euphoria. Sleep paralysis for example. It happened to me once and it made me see things differently, nothing religious or mystical, just an enhanced perspective.
To give an example, during my episode I had what is usually described as an out-of-body experience. I felt myself walking around my bedroom as if I were awake, only to find out that my body never left the bed. Now if the sense of being "out of the body" is an illusion, how can we be sure that being "in the body" is not just the same illusion? (I'm tempted to think we are not anywhere and that space itself is the illusion, but that is beside the point)
One can easily arrive at the same insight (i.e. being in the body is just an illusion) without actually experiencing it. Of course, if you have such an experience and you get knowledge or inspiration from it, so much the better. But to say that theorizing about consciousness is a waste of time if you haven't experienced altered states is myopic.
