I was eight years old when this originally aired in the U. S. It very much resonated with me. Of course, I loved any kind of science fiction at that age, and still have a fondness for it, although I'm of course much more discriminating now. The show was set in the then far off year of 2000. Like many other such depictions, it was quite optimistic about what things would be like. Future society was depicted as full of automation (robots were commonplace), flying cars, space travel, an overall high level of prosperity, etc., which of course instantly appealed to me, but what really captured my imagination was the character of Astro Boy himself. He was immensely powerful and could fly, but he was also smart, heroic, kind, sensitive, and caring. He was my ideal of what a boy should be, and it didn't matter that he was a robot. The show advocated giving robots rights as sentient beings. I remember writing an essay in school about him.
Back then, I paid no attention to the low frame rate or the crudeness of the animation, and in retrospect, they never were what mattered. What mattered was the sense of wonder and thrills and empathy for a character who was superhuman, but wanted love just as any human does.