The people of Earth have barely begun to explore what lies beyond their world. Their space age is in its infancy compared to most of the other races that populate the galaxy.
The Doctor can’t interfere too much, give them a leg up so to speak; that would mean interfering with timelines, which is the one thing he knows he must not do. But the odd human here or there can’t significantly influence humanity’s progress. All he’s doing by taking his companions on their own personal voyage of discovery is igniting a spark.
What happens afterwards is up to destiny.