> these ancients having incorrect understanding of language, psychology, and metaphysics, caused them to make grave mistakes
That is absolutely and staggeringly wrong.
It maybe the case with some of the ancient Western Philosophies (objective, analytical), but certainly not the case with Eastern Philosophies (subjective, experiential). "Human Condition" has not changed but only the context in which it is experienced and expressed has changed.
Read at least the three schools of Indian Philosophy i mentioned above. S.N.Dasgupta's multi-volume A History of Indian Philosophy gives a very good non-trivial starting point for the serious reader.