I think knowledge isn’t something that accumulates—each generation discards some old things and discovers some new.
The old stuff is still there of course, but it’s not a part of the societal discourse or understanding and so is more inert information than knowledge.
Nietzsche, in his book Beyond Good and Evil, says that Plato is the beginning of a great decline, responding with his tragic view: 'And who said that man is capable of knowing the truth? [...a long waste of time follows...]'. I recommend looking into the discussion of universals, as I understand that much of the disagreement stems from this point.
The old stuff is still there of course, but it’s not a part of the societal discourse or understanding and so is more inert information than knowledge.