I think we should stop using the phrase "Roddenberry's Vision" and try "Star Trek's Vision."
You'll notice I did do that lol

I honestly don't think he was the L. Ron Hubbard of the thing anyhow. WE are the source.
All that high-minded "evolved humanity" Utopian thought was just some self-serving hokum that he cooked up for the convention circuit years after the fact of the original Star Trek.
My take on it is that it was the positive impression it left on viewers of the 60's & 70's which fed the whole thing. That a tv show about the future depicted a harmony & equality of genders, nationalities, & ethnicities, rarely seen before in American entertainment, that it showed we could rise up from the ashes of the dark path we were on, & advance the species into unknown wonders, had a profound effect on not only tv viewers, but the culture as a whole. It was this phenomenon that I believe probably affected the man himself.
Years of being told how the show had influenced real scientists, world leaders, & people of every walk of life, has a way of inflating a person's ego, I'm sure. They named an actual space shuttle Enterprise, & all those people were there too see it. By the time TNG had come around, it was no longer just a quirky space adventure they were making. It was a legacy they were passing on, & that legacy was the hope of a bright future, which I do really think Gene ended up taking to heart, for good or ill.
It didn't take too well in the cinemas, & they ended up shutting him down & trying to bring back what people loved about the show, the adventure & drama, & he probably didn't care for that direction they took, because he wanted it to be the thing everyone was dreaming of.
Little did he know, that Utopia? Makes for boring tv & movies, & as much as I love TNG, that aspect of it can definitely become tedious & cumbersome, not to mention inconsistent. Don't hate on him too much though. He just got swept up in the hype. Who among us wouldn't? For god sake, MLK told Nichols she shouldn't leave the show, because it was that important people see her there. That kind of thing might get under your skin a little, make you think you have an obligation to right the world through your little sci-fi play