It Makes a Difference
There's an old Western movie that has a scene of an Indian (Native American) standing next to a "white girl", behind a fallen tree (so you cannot see their feet). The Indian pulls his knife out, lunges in the direction of the girl, she falls down dead. The Indian then notices that some white folks have seen him, so he runs to his horse, jumps on it and rides away as fast as he can. The white guys mount their horses and give chase (without bothering to check on the girl). I don't remember most of the details, but it turned out that there was a poisonous snake approaching the girl and the Indian saved her life by stabbing the snake, and she fainted from fright and was not dead at all.

Lucky for the Indian that he stayed alive long enough for the truth to be discovered. But I digress. Trust me - there's a MASHAL brewing.

The written word of the Torah and the plain meaning of the text often convey to the reader a false picture of what is going on. Yaakov is cooking a lentil dish, Eisav returns from the field exhausted and hungry and asks his brother for some of the lentils. There is a fallen tree that is blocking our view of what is really happening. Would you believe that Yaakov was preparing a mourner's meal for Yitzchak, because Avraham had just died? Would you believe that Eisav had just murdered someone, worshiped an idol, and committed other sins, making him totally unfit to serve as the pre-kohein (that was the function of the B'chor) at his family's altar? This aspect of the birthright needed to come to Yaakov. With these details, we see the story from To-l'dot in a very different light.

These details were NOT dreamed up by an imaginative commentary who was looking to besmirch Eisav's reputation and portray Yaakov in a favorable light. These details are part of the Oral Tradition, which was revealed together with the Written Word and past down through the generations. They (the details) are part of the primary story.

This could be so even when there are different opinions. When Rashi looks at the meaning of No'ach was righteous in "his generation", he brings two points of view: No'ach was so righteous that even in his wicked generation, he was righteous, how much more so would he be in a "normal" generation.

Or, By comparison to his generation, he was righteous, but he would not necessarily shine in a generation of good people. It is very possible that the Oral Torah on the text contained both ways of looking at it. And they don't contradict each other, even though they are opposites. Because we need to look at No'ach's situation in both ways. And apply lessons for ourselves from both perspectives.

To put it simply, if the Gemara says it, then it is so. And whatever "it" is, it becomes part of the Tradition. And this doesn't end with the Gemara. There are many sources of Oral Torah that input into our Traditions.

All of the above is part of a broader concept - namely, that it is IMPOSSIBLE to understand the Written Word of the Torah without the Oral Tradition and Law. It cannot be done.