נח איש צדיק תמים היה, בדרתיו. את האלהים התהלך נח.
Noah was a righteous and whole-hearted man in his generation; Noah walked with G-d. - Genesis 6:9
This passage in Genesis calls Noah a righteous man (צדיק). The word צדיק is not thrown around lightly in Judaism. Think of it as analogous to the "one percenters" of Jewish spirituality. Noach was righteous enough where he and his family were the only ones on the planet spared from the Flood. Noah is also referred to as תמים (whole-hearted). The word תמים can also mean unblemished or simple, which brings up some ambiguity. The word תמים, however, is generally viewed in a positive light in this verse (also see Psalms 15 and 101:6). You would think that Noah's status is unblemished and beyond reproach. However, there is a clarifier that casts doubt on Noah's righteousness: "in his generation" (בדרתיו). This caveat is so important that it caused a debate amongst the rabbis.
The phrase בדרתיו can be used to argue either in favor of or against Noah. One can argue that because Noah prevailed in such a corrupt society, Noah would have been, a fortiori, even greater had he lived in another generation (Rashi; Resh Lakish in Talmud, Sanhedrin 108a). On the other hand, one could argue that only by comparison to the rest of his generation was Noah righteous. Another way to say this: If Noah had lived in another generation, he would not have been considered righteous (Ramban). Which one is it? Was Noah adequately righteous or was his righteousness merely relative to his contemporaries?
One can argue that being average in absolute terms during such a time of such depravity is precisely why Noah is referred to as righteous. This is why R. Eliyahu Kitov argued that the righteous of each generation ought to be judged in the terms of their own time (Sefer HaParshiyos). Even so, this solidified why I am inclined to believe that Noah's righteousness was relative for three reasons. One is that Noah walked with G-d. As Rashi points out, walking with G-d meant that Noah needed G-d's support to spiritually advance. Conversely, Abraham walked in front of G-d (Genesis 17:1), meaning that Abraham's righteousness was good unto itself. The second reason for thinking his righteousness was relative was how Noah reacted after the Flood. My take on Noah post-Flood is that he was dealing with a combination of PTSD and coming off a spiritual high. Noah built the ark and survived the Flood. His mission was complete. He ended up building a vineyard (Genesis 9:20), getting drunk (Genesis 9:21), and according to the Talmud (Sanhedrin 70a), was either castrated or sodomized by his son. Noah fell low enough where his sons were ashamed to look at him (Genesis 9:23). Needless to say, Noah did not handle his emotions well post-Flood. If Noah were that righteous, he would not have faltered the way he did.
The third reason is even more intriguing: Noah did not protest G-d's verdict nor did he attempt to save his contemporaries, which is contrasting to Abraham's response to Sodom and Gomorra. This reason is implied in the Talmud (Shabbat 55a) and explicitly stated in the Zohar (Zohar Mashatot, Bereshit 254b). According to the Zohar, Noah did not attempt to save a single person or beg G-d to change His verdict. The Hebrew for Noah (נח) has the same root for the word "comfortable" (נוח). While it is true that Noah did not harm others and he was able to withstand corruptive influences of his generation, he did not do good towards others. This is why in the Zohar, G-d calls Noah a "foolish shepherd." He receded into his comfort zone. In terms of individual responsibility, Noah was fine. As for collective responsibility, Noah did nothing to contribute to the betterment of mankind. The Golden Rule is important and vital. It creates a basic respect for humankind. However, that is not all we are here to do. Certainly from a Jewish point of view, a spiritual vocation does not mean isolation or a monastic lifestyle. It means contributing to the world so that it is better than when you found it. This lack of responsibility towards others is why Noah's righteousness comes with a big caveat. If we want to avoid the downfall of Noah, the righteousness we express through our thoughts, words, and deeds cannot be in isolation and cannot be done strictly for our own benefit. We need to help others, and by doing so, can we truly live a life towards righteousness.