Sounds like you haven't read much, gee. What a strange comment. It has a far higher signal/noise ratio than modern philosophy, I'd say, maybe because usually only the best has survived.
You can look at it this way: every possible statement seems to have been made by at least one ancient philosopher, especially once you include the non-western traditions. There were atom-ists, and continuum-ists, and so on. If you view ancient philosophy as one big bucket of sentences, it will fill up sentence space fairly uniformly. You could reconstruct ancient philosophy just by coming up with reasonable-sounding claims about things they were aware of back then until you ran out of possibilities, although that wouldn't produce the historical association of certain views with certain people.
A distribution that uniformly fills space is, in the technical sense of the word, "no information." If you trim it down (for example by doing experiments and discarding whatever doesn't match your newfound knowledge of reality), you get a distribution that "has information."
To put it concretely, finding out that an ancient philosopher said something doesn't help, because ancient philosophers said everything they could think of. Whether that is better or worse than what philosophers are doing now is up to philosophers to decide, I guess.
However, new sentences are made every day, new words made very often. Nobody cares about the technical sense of the words "no information". If your argument was extended from 'ancient philosophy' to 'anything ever said by humans', then anything ever said by humans would fill the sentence space fairly uniformly, so finding out that anyone has said anything doesn't help.
A single human has not considered and thought about every sentence possible. They have their own beliefs and knowledges, and by reading ancient philosophy, they can expand that knowledge base, change those beliefs. Ancient philosophy is not inconsequential, and it certainly contains "information".
He did arguably explicitly predict that basic mathematical/geometric forms underlie the structure of the universe. E.g., that atoms would be composed of pyramids, cubes, dodecahedrons and that the behaviour of atoms would be based upon the different geometric properties of basic forms.
That idea is only partially correct, however. Atoms are based on the basic mathematical forms -- but on the spherical harmonics of electron clouds, not point geometries. Whoops! Otherwise, the idea is commensurable with modern atomic understanding.
Earth, water, air and fire correspond not to elements (ice can melt, obviously) but to phases of matter. (Solid, liquid, gas, plasma).
There is a reason Classical Greek philosophy underlies western civilization. They were not dummies and there is still a lot we can learn from them. It's not like all their ideas were examined in the 1800s and we took all the good ones, leaving the classics as a sort of intellectual skin worth shedding. Instead, it is the core we build on. It's worth understanding the core -- and giving them the benefit of the doubt to identify interesting ideas.
Like that the universe begins with "the one" :)
That's accurate, though. If I told you a statement and backed it up with the claim that "at some point in history, a human said it" then you really haven't learned very much. Likewise, if a statement is tagged with "and by the way, an ancient philosopher believed it," you may have learned something about history, but the statement itself hasn't gotten any more believable.
If you apply the same principle to all of language then you could say language has no information. Try it with a dictionary, the words are distributed pretty uniformly, does the dictionary have no information?
Same for the whole universe.
So are you saying that "information" only exists when some arbitrary observer (in this case you), applies some sort of filter or boundary to what they are looking at?
That is not true at all: the dictionary is highly concentrated in correctly-spelled English words. If the dictionary was evenly spread over the space of sequences of letters A-Z it would not be useful at all, because next to Cat would be Cas and Cau.