Like the M*A*S*H reference.
It's true that since original Trek was the only real example of a well-done science-fictionish (non-anthology with regular characters) show back then, that satisfied the requirements of escapist space adventure as well of those of more adult SF drama, it became the focus of a huge fandom. In more recent years, these different kinds of fans might have latched onto different shows.
I don't think this makes original Trek any less great a program, though. I think it helps to show how great it was, to draw in so many different types of viewers.