Rabbi Lord Jonathan Sacks explains that the point of debate between the two views about the phrase that Noah is righteous "in his generations" is whether Noach was a loner and individualistic by nature or by necessity. 

Parashat Noach begins by describing Noach as a righteous man “be-dorotav” (“in his time”), and Rashi famously cites two views among Chazal in explaining the precise implications of this term. One view interprets “le-dorotav” as underscoring Noach’s unique stature of piety, noting that he lived a virtuous life despite living in a world of sin.  If he had lived during the time of Avraham, when he would have been able to surround himself with likeminded God-fearing and ethical people, he would have been so much greater.  According to the other view, however, “le-dorotav” comes to qualify, rather than magnify, Noach’s piety.  It emphasizes that Noach was righteous only in relation to his corrupt contemporaries, whereas if he had lived among other righteous people such as Avraham, he would not have been regarded as righteous at all.

            Rabbi Lord Jonathan Sacks explains that the point of debate between these two views is whether Noach was a loner and individualistic by nature or by necessity.  According to the first view, Noach was not naturally introverted, but was forced to withdraw from society to protect himself from its morally toxic influence.  Hence, if he had lived during the time of Avraham, when he could have come under the patriarch’s influence of piety, he would have been far greater.  The second view, by contrast, maintains that Noach was naturally withdrawn, and this – and only this – enabled him to avoid the corrupt influence the pervaded the world at that time.  Therefore, living in a different era would not have helped him grow or advance any further.  Noach was who he was, and thus he would not have stood out in a different era as he did during a time of widespread evil and depravity.

            Underlying this discussion is the basic premise that we should, ideally, be constantly looking for sources of positive influence.  Noach withdrew either due to unfortunate necessity, or because of a personal weakness that would have stifled his growth in a different era with available sources of positive influence.  According to both opinions, withdrawal is, as a rule, to be discouraged.  Unless it becomes absolutely necessary, we are not to live in an “ark” isolated from other people, but are rather urged to engage with them so we can influence them and in turn be positively influenced by them.  If we remain isolated and withdrawn, we deny ourselves valuable opportunities to impact our society and to further our own personal advancement by exposing ourselves to people worthy of our emulation.