The first Gallifreyan time machine, the Time Scaphe, was powered psychically rather than technologically. (PROSE: Cat's Cradle: Time's Crucible) The Archons claimed that the Time Lords didn't discover time travel for themselves, but developed it after they declared war on the Archons and stole their technology. (PROSE: The Nameless City)
At various points in its long and very varied history, the human race questions where it's going – what it might become. And, sometimes, they worry that they've come too far from whatever they were before. Every highly evolved industrial society, on every planet, throughout history, creates a group who reject that technology. Who choose to live a life outside the cities, close to the earth. They might be religious, political – maybe they're just following a dream of ancestors. Looking for an Eden. I don't know. But they think it'll bring them closer to what it means to be human.