Noach was not perfect tzadik because he didn’t save the world

 Emes L’Yakov (Bereishis 06:09) Why do some of our Sages say negatively that  Noach was only a tzadik in his generation when it is possible to interpret this verse as praising him? A possible answer is that he was viewed negatively because he was not able to save his generation  Meaning that if he were a complete Tzadik, he would have saved them This can be explained by Bereishis Rabbah (31:03) which says that he chastised them as idolaters when in fact they were fully aware that idolatry was nonsense and they only worshipped idols as an excuse for sexual immorality as is stated in Sanhedrin (63b).Thus his preaching was useless in changing them. That is why some of the Sages viewed him negatively. because of his lack of awareness of the true situation – even though this seems more of a lack of wisdom then piety  We see from this that lack of wisdom must mean a lack of piety. This means that if he were really concerned with Truth, he would have known to chastise them concerning sexual immorality. Thus the foundation of serving G-d is being concerned with putting all one’s efforts in determining the underlining Truth.