Back in 1968, it was the buggy whip generation who had doubts that it really happened. In 2019, it seems to be the 35 and under crowd who call it a hoax. My instincts tell me that they can’t bring themselves to believe that something so great, awesome and amazing could have happened in a world where they had not yet existed.
We watched the moon landing at my grandfather’s house and he did not believe it was real. He was born in 1888 and had a remote ranch in Colorado. By 1969 he had moved to town (population about 600) to be closer to doctors. He was still dealing with the idea of television. I think it was really hard for him to accept how far technology had come in his lifetime. Horse and buggy generation as you say.