"Behind the veil of maya, the brick is still ultimately a brick"

That's a pretty big assumption - a common one, of course, that many of us make. Most of us operate under the assumption that there is something like objective, persistent reality, but none of us really know for sure. It's a rule in the game we're playing.

at some point they inject false input built from randomised activation into one layer of the chain and make the whole thing no longer correlate to actual real "stuff" in the outside world.

If we take LSD and start to smell a painting, or smell "Stairway to Heaven", how is it any less a valid interpretation of the sensory input? Especially with the senses of smell and taste, which appear to be especially arbitrary - if you start to see a visual representation of the smell of spearmint, how is it any less valid? How is it any less valid than say, a spectrogram of a song?

The idea that drugs such as LSD are useful for "expanding" consciousness is thus terribly flawed

Is it possible to get a different perspective on something, and not expand your consciousness? If you have one way of looking at the world, take 300 ug of LSD, and come back with a second perspective, which you can access at any moment after that event, willfully choosing between the two, or even combining them, would it be incorrect to say that your consciousness has been expanded?

and can often cause serious psychological problems.

I think the information you have about the risks has probably been greatly exaggerated. Psychedelic drugs tend to have some of the lowest risks.

For me, i'll stick to movies, books and video games though - at least I can keep firmly in control with those.

There's nothing wrong with not having an interest in psychedelic drugs, but a famous phrase comes to mind - "People who say it cannot be done, should not interrupt those who are doing it."

Have a good one