The thing that most interested me about Star Trek was the social justice and equality in that fictional society, and it was plainly obvious. [snip]

Roddenberry clearly had a vision of a much more progressive society, but he had to work within the cultural presumptions of the time...or the show would never have been accepted by the Network and no one would have ever seen it.

I'll back up a little here. I agree that Picard was a better actor in the role he played than I thought Shatner was in the Kirk he played. But, the first program was remarkable, as you say, for the amazing amount of philosophy and mythology that made it into the scripts. It set a standard that the others improved upon and that many other programs couldn't begin to touch.

Big differences between that two that we see particularly clearly from this distance are the production values. The early one, to quote Spock, was "stone knives and bear skins" to some of the series that followed. (And after the first series Roddenberry must have ended up with an amazing collection of salt and pepper shakers. That's what they used for many of the odd electronic hand tools in the programs. Sounds were added so you'd think they actually did something).