I am still deeply impressed that we got 12 men on the moon, and an additional 13 to orbit the moon (2 men went twice), and back alive, using 1960s technology.
First of all, the NASA engineers were geniuses. All of them. The concept, the design, the construction, the execution. All of it.
Second, the astronauts were incredibly brave
Third, politics was never an issue that interfered with the missions. They survived the Johnson and Nixon administrations - two of the worst presidents ever.
Fourth, quality assurance was WAY ahead of its time. With little redundancy and mostly no escape systems, everything had to function perfectly.
And it will STILL be a challenge to repeat this feat, 50 years later.
I suspect the politics will be the greatest impediment to a successful return to the moon.