The Idea of Time Travel in Science Fiction

Image via WikipediaI was reading a blog (TechRepublic) the other day and they had a list of the worst science fiction television series ever. I had to laugh at the listing of Star Trek: Enterprise because, well, it is true! I am a die hard Trek fan and I did watch the entire series even though I got lost in the "Expanse" and did get lost in this quest for the Xindi and why that story arc had to consume the entire third season. Then just as abruptly as this trek started it ended in the fourth season. The fourth and final season was better than the rest because it did tie up some loose ends about the history of Star Trek, which in my opinion does stay surprisingly consistent. One loose end was the Klingon physical features between the Original Series and The Next Generation and this explanation was nicely played out, the work of Dr. Soong with positronic brains forged a nice bridge to the Next Generation, and the formation of the Federation was explained as it had not been in the Original series. The very last episode of Enterprise was a complete disappointment with the implication the entire series was a "hollow deck" program.
One of the opportunities that I think they missed out on was the Temporal Cold War. I like the idea of time travel but do not know enough about physics to attempt to understand time dilation in terms of special relativity and general relativity and gravitational fields. I do know that I like the idea of time travel. In Enterprise, beings from the future were able to travel back in time and alter the time line. There were two factions who were at war with each other and trying to change events in their favor and beings from further in the future who were trying to be the moderators, if you will.
This topic could have led to very intersting stories because some of the time travelers were so intermixed with other species that it could have brought up the discussion of acceptance of others who are different from ourselves and who choose to create families and have children who then go on to have relationships with other species because they are brought up in an atmosphere of acceptance. The beings evolve until it gets to the point of not being able to indentify one dominant species. I find this very interesting and very relevant in our own time.
Another storyline could have been the alteration of time lines (which never seemed to occur in the story) and what difference that would have made in earth history.
It is easy to sit here and look back and say oh, they could have written this or that, but there really were some missed opportunities. It may have been the times, the studio heads, the producers, who knows, but I would have really liked to see more of the Temporal Cold War in Star Trek: Enterprise. Sometimes intelligent stories couched in sci fi can teach people about basic science and social and psychological issues. That is the kind of science fiction that really turns me on.