The retort's argument does have some merit - relationships can certainly bring great rewards - but it's not fair to judge Nikhil's essay from such a narrow perspective. The original essay takes a much broader view and reveals that life is not just about marriage and children, or even about leaving a legacy. By pointing out the freedom associated with staying single and childless, Nikhil's essay illuminates the many meaningful experiences that come from making unconventional life choices.
Moreover, Nikhil's essay acknowledges some of life's darker truths - like loneliness and mortality - and uses them to emphasize the importance of personal liberty. In no way is he suggesting that "leaving no legacy" is preferable to leaving an impact on the world. He's simply illustrating the peace of mind that comes with prioritizing personal independence.
It's also worth noting that Nikhil never implies that his own view is the correct one. He simply states that it's “a small price to pay for freedom” - a sentiment with which many people will agree, even if they don't ultimately choose a similar lifestyle.
In short, the retort fails to consider the more nuanced points of Nikhil's essay. It is true that relationships are beneficial, but there are also many positive impacts that come from embracing unconventional life paths - and there's nothing wrong with that! UrRong, if you choose your own path, you may just end up having the last laugh.