Here is the context: "Millenia ago astrology was as close to science as you got." Does thr sentence mean that people nowadays consider astrology to be a science as they considered in the past?
It means that thousands of years (millenia) ago there was no science. Astrology was not science, but it was the thing that was closest to science. It implies that astrology is not considered to be a science nowadays.
The word "you" in "... as you got." is the impersonal you. It doesn't you "you the reader". It means "an unspecified person". In formal English the expression "...as one got" would mean the same. "Getting close" is used figuratively, to mean "be similar".
Many years ago there was no science. But some things were similar to science. Astrology was the thing that was most similar to science.
For example :
Millenia ago a dinosaur steak was as close to a MacDonalds Big Mac as you got.
A dinosaur steak isn't a Big Mac. In the past people didn't have any Big Macs, but dinosaur steak was in some ways similar.
But there is a secondary meaning. You know that a dinosaur steak isn't very much like a Big Mac. So the sentence implies that many years ago, there was no Big Mac, and nothing that was very similar.
Similarly, the original sentence also implies that many years ago there was nothing that was very similar to science.