Stargirl tells us a great deal about our ancient past as humans, and how connecting to that past can help us understand ourselves better. By focusing on these remnants of the past, before we created planes, trains and automobiles, we may learn some interesting things about the universe and ourselves as humans. That's what Stargirl does, and it brings her great joy and meaning. That's what Archie does, too, and he seems quite content with his lot in life. We can't forget that we come from the earth and will return to it, too. Or at least that's what Stargirl would have us believe.
Stargirl is no star person. And she's not any more connected to the past than the rest of the characters. Archie just says all this to explain away her strangeness.
Stargirl's deep connection to the past is what disconnects her from the present moment. The girl can't make a friend because she's too busy daydreaming about cacti and dead birds.