Ah but you are assuming technological advance coincides with general human advance. Understandable error. How do we know an "advanced" society can evolve to a star trek like existence. Perhaps it's more Ferengi than Starfleet. Perhaps governments are no more honest than today and discover they can manipulate the past to benefit the future, or in other words, the present. Would those governments resist the temptation?
Ah! But there have been naysayers throughout history, and not just armchair skeptics. A leading British Royal astronomer once said that transatlantic ocean crossings by heavier than water steamships would be impossible. He said that rough North Sea and Atlantic ocean would swallow steel ships. The same person said that we might as well fly to the moon.
Another scientist balked at heavier than air craft and said talk of mechanical flight from New York to Los Angeles in a few hours would never happen.
In just 50,000 years or so man has progressed from using stone tools to landing on the moon. It's a relative blink of an eye and tiny slice of time in the evolutionary scheme of things. Technological advancement is a given in our own example. Like biological evolution, tech advancements are just a matter of time. Kardashev and Dyson described how civilization with economic growth rates average one percent per year would have certain energy requirements. At some point fossil fuels either run out and they die, or it forces the civilization to develop new and sustainable energy sources. From certain assumptions they calculate advancement from our current type 0 status to that of type I in about 100 years. Type II(Federation in Star Trek) in just a few centuries. Type III(Empire from Star Wars) in about a thousand years. Type IV in just a few thousand more. Who knows if type V or VI(God-like) exist? Can we doubt Darwinian evolution and technological progress?
Truly if time travel were possible it would have been done, that we have not seen it means it is not possible.
Behold! This is but one story of abundant circumstantial evidence for... time travelers? Travelers from "another world"?:
Roswell New Mexico, 1947.
And some say there have been other close encounters around the world. Some western world governments have been more transparent to the public than others with respect to disclosure of information. Some of us ask, why does the U.S. Government not simply announce it if true? harkening back to 1947, the beginning of the cold war, the U.S. Government released four different stories about the Roswell incident:
1. A flying saucer
2. A radar reflector and weather balloon
3. A Mogul balloon train over 500 feet long with 23 balloons, sonobuoys, etc.
4. And most recently, a Mogul balloon train plus crash test dummies dropped at least six years AFTER the 1947 crashes Southeast of Corona and West of Magdalena.(Stanton Friedman)
Well, which was it? Canadian physicist Stanton Friedman says that the U.S. Government and especially the C.I.A. have been lying to the public about Roswell for a long time. Which of the above four scenarios is the truth? Skeptics have said that the first report by the U.S. Military was made by a flunky who didn't know his job. But as Canadian Stanton Friedman says, that wasn't true, either.
OTOH, why wouldn't they tell the truth? Why wouldn't the U.S. Government or U.S. Military simply say, Hey, yeah, we found a crashed disc. And by the way, there were aliens aboard the craft just as dozens of eye witnesses have reported since 1947. And another by the way, these things are flying in USAF and NATO air space all the time, and there isn't a darned thing we can do about it. Why wouldn't they just say that?