At the risk of derailing the thread into a Trek conversation - Roddenberry had three big failures of his vision of the future:
1. The absence of gay people as noted above
2. That religion would be dead by the 23rd and 24th centuries.
3. Capitalism would be dead by the 23rd and 24th centuries - essentially wiping out our natural human instincts to have what we cannot.
All are not plausible visions of the human species - past, present nor future.
1) It's been a while since I've discussed Trek in any depth, so I might be wrong about some of this, but...
A positive onscreen depiction of gays would not have flown on 60s TV where they gave him a hard time about women in command positions and even aliens, nor do I think he would have done it voluntarily then anyway. With the exception of TMP, I believe Roddenberry had very little day-to-day involvement with the TOS films and was dead for the TNG ones. He was only heavily involved in the first two seasons of TNG, IIRC. So, while he could have done something in the first two seasons of TNG I suppose, the bulk of that failure rests on his successors, especially with them running the shows in an era where positive depictions of gays on TV were becoming much more commonplace.
That being said, a lack of clear depiction of gays doesn't mean a lack of gays in the universe, and there were occasional subtle references made to it. There was the episode with the Ferengi female dressed as a male to succeed in business whose crush on Quark Dax encouraged while she believed the Ferengi was male, for one example.
2) There are several instances of religious practices and numerous references to religion in TOS, TNG, DS9, VOY, and ENT, so that's not factually correct. The lack of people being in your face about religion does not necessarily imply its absence. The stated positions on religion of prominent characters like Picard does not imply that everyone agrees with him any more than my atheist opinions imply that everyone agrees with me.
However, if Roddenberry as a secular humanist wishes for his show to imply that religion is dead, why does that represent a failure on his part? It's speculative science fiction. He's creating the world he believes people should aspire to, not the one that's supposed to be the most realistic. Trek isn't known for its hyper-realism.
3) Again, not factually accurate since there were numerous examples of and references to capitalism in Trek. There are as many references favoring capitalism as there are opposing it. Trek was never really consistent on the issue. Humans seemed to have eliminated capitalism in their own society but it's still needed when dealing with many other species who haven't.
That being said, again it's not a failure if that was what Roddenberry wanted human society to become. There's no requirement for being enslaved by realism if your goal is to create a utopia for people to aspire to.
On top of that, while I agree that neither religion or capitalism are likely to go away in the next few hundred years in reality, the human species in Trek has gone through a lot of things we haven't that would vastly change our worldview. Genetically engineered humans, artificial intelligence, global nuclear war, faster-than-light travel, finding thousands of habitable planets, finding thousands of alien species, cryostasis giving you the opportunity to live well into the future, time travel, post-scarcity economics and replicators... To say that those things would not fundamentally alter human society is a bit short-sighted, don't you think?
I wish we had this discussion a few years ago when I still discussed Trek regularly. Now I feel ill-equipped since I don't remember most of the references I would have used in a debate like this.
