Parshat Noach opens with an enigmatic description of Noach. "This is the history of Noach, Noach was a righteous man, flawless in his generation. Noach walked with G-d".
The Malbim brings Genesis Rabbah 30:9 where R'Yehuda says that Noach was a righteous man in his generation but had he lived in the generation of Moshe or Samuel he would not have been called a Tzaddik.
R' Nehemia, on the other hand, focuses on the fact that Noach was indeed called a Tzaddik. Therefore, he reasons, that if he was able to remain righteous in a generation of wickedness, where there was no one to emulate, then he would surely have been a Tzaddik in the generation of Moshe or of Samuel.
Rashi says that had he lived in the generation of Abraham he would not have been considered significant based upon the same Medrash. Furthermore, Rashi says when the Torah says "Noach walked with G-d" this is in stark contrast to Abraham where the Torah says, "(G-d)before whom I walked" (Breishit 24:40) – implying that Noach required G-d's support to uphold him in his righteousness, whereas Abraham strengthened himself by himself and walked in his righteousness by himself.
Noach was considered a prophet. He spoke with G-d. Yet, it seems he could not attain the level of Abraham or Moshe. It also seems his reserved nature and personality prevented him from attaining their lofty spiritual status. Those among the sages that interpret "flawless in his generation" to discredit him believe he did not do enough to change G-d's Decree to destroy the world.
Unlike Abraham who tried to save Sodom by pleading with G-d, Noach did not plead with G-d in a similar way. When G-d was going to wipe out the Jewish People after the sin of the Golden Calf, Moshe pleaded with G-d, "Turn from thy burning anger and change thy mind about doing harm to thy People" (Exodus 32:12-14).
Noach appears more passive and reticent. Whereas Abraham went out of his way to bring people closer to G-d even when he was ill after having had a circumcision, Noach did not. Noach had 120 years to change people around him and bring about a Teshuva movement. He did not. Yet to his ultimate credit he saved the world and humanity.
The lessons are dramatic and everlasting. Even though Chazal consider Noach a righteous man, there was so much more he could have done. It brings to mind many great men who accomplished much but could have done so much more.
One contemporary example is that of Franklin Roosevelt. President Roosevelt may ultimately have saved the the world by entering into World War II. However, many lives could have been saved had he entered the war sooner. As great as President Roosevelt may have been, he had many opportunities to save Jews from the gas chambers but did not do so. He refused to bomb the railroad tracks to the concentration camps. He knew fully well Jews were being killed in the millions by the Nazis but he did not do anything to stop it till it was too late. Even President George W. Bush on a visit to Yad Vashem in 2008 said "America should have Bombed It" referring to the train tracks to Auschwitz.
Like Noach, Roosevelt could have saved many more than he saved but failed to do so. There are valuable lessons to be learned for the generations from the story of Noach. It is quite possible that Abraham ten generations later took these lessons to heart and changed History. It is up to each and every one of us to do the same. Shabbat Shalom.