I would at least have expected an observational data point - doping with LSD, the same way we see widespread doping in many professions (including creative ones) with amphetamines/Adderall. But no, I mostly see use by creatives "stuck in a rut", with a wide gap between what they perceive ("LSD helps me getting more creative", "I had a breakthrough", or the more extreme "it opened my mind to new realities") and objective reality (mediocre work). You don't see "the best works of this artist come from his LSD period".
You see another type/style of work (... usually "psychedelic"). You dont see groundbreaking stuff in the general, universal term, despite all the stuff about "a higher plane of existence", "opening the mind", "being one with the universe".
I think the closest thing I know about is Harman and Fadiman's 1966 study where they gave mescaline to a diverse group of professionals to see if it could help them find creative solutions to problems they were stuck on at work. Apparently it worked! It was meant to be pilot project to launch further study, but instead the research was shut down due to tightening federal restrictions
https://journals.sagepub.com/doi/abs/10.2466/pr0.1966.19.1.2...
Have you considered that, when people reach for LSD while "stuck in a rut", their output should really be measured against that baseline? I mean, going from "I can't do anything" to "I can do mediocre work" is a fairly big improvement.
That said, in general, I would agree that the long-term effects of LSD on one's abilities are not all that profound. What it does, mostly, is making you more aware of things (or rather connections between things), centered on yourself. Whether this actually leads to any improvement depends on what one does with this information, but, well... how many people drastically change their lifestyle after being told by a doctor that they should do so? Same applies here.
As far as doing things during a trip, this can go either way. LSD takes one's "pattern matcher" up to 11, basically. This means that you can easily spot actual patterns that are there that would take you a lot of time in a normal state of mind, but it also means that you start seeing clear patterns in random noise. Since either manifest as intuition, the only reliable way to distinguish them is by rigorous methodical testing, which can be done, but during the trip it's basically swimming against the current, so generally, people don't. The quality of the output then depends on the input (i.e. on whether there was an actual pattern to find or not, and on how much random noise there was in the environment). It's no wonder, then, that this averages out to mediocre.
But I do think that actual quantifiable improvements could be achieved with strict adherence to a "trip protocol" scientifically developed to optimize for that. Those wouldn't be fun trips, though! And, of course, you'd need to develop such a protocol first through study, which is difficult when it's such a tightly controlled substance.
Sorry, my writing isn't as good or clear as I wish: my beef is with the mystique around LSD opening "the gates of reality" - extraordinary,above normal claims. That's why getting from a rut to mediocre when you were once great is not what I had in mind.
Let's be honest: if people have been talking so much about LSD for so long, it is not as an aid to get back to mediocre.
I think you're overly focusing on one particular subset of people talking about LSD. I can assure you that "getting back to normal" is a very common motivation for many, and they do talk about it. It's just not the kind of talk that you see making sensational headlines.
The "gates of reality" stuff is more complicated. Quite a few people interpret it in a very... religious sense. Like your mind literally "connects" to some other place or entities that actually physically exists and can grant one powers. I can totally see how people who are religious, or already into various esoteric spiritual practices, or even just raised in a culture where such themes are common, can have that takeaway from a trip - what they see is their own consciousness reflected, but if they are already primed to believe in such stuff literally, it can be very convincing. But, conversely, there are many people that are perfectly capable of understanding that the ultimate source of all experiences on a trip is one's own mind; "opening the gates" then can metaphorically mean better awareness of oneself and one's interactions with the world at large, but I can't think of any way you'd be able to quantify that externally.
You see another type/style of work (... usually "psychedelic"). You dont see groundbreaking stuff in the general, universal term, despite all the stuff about "a higher plane of existence", "opening the mind", "being one with the universe".