Dear Hitman,
I hope to convince you with the following essay that Nadal has indeed had an era. As a matter of fact, to convince you that Nadal's era is the longest tennis era in the history and that we are still living it, no?
First of all, I think it is a given that Nadal's supremacy and unprecedented domination of clay tennis is not what is being discussed here, as that is beyond any doubt. Instead, it is his achievements outside clay which should be qualified and quantified insomuch as it is in the light of those achievements that we must appraise his overall importance in tennis history. Rather than construct a set of paragraphs to bore everybody and make me think too hard (or think at all) I will provide some bullet points below for your consumption.
1. Nadal has 7 slams in his worst surfaces, in an era where he had to compete with two GOATs in those surfaces. Neither Federer nor Djokovic even approach those achievements against Nadal at Roland Garros, where he has been largely untouchable. So while you might argue that 7 non-clay slams is an unimpressive tally, it is rather the opposite when put it into context.
2. Nadal suffered the blunt force of Federer and Djokovic's peak games. You could strive to argue the same in the case of Federer and Djokovic, but there are subtle differences. Federer had already won 10 or 12 slams before Nadal and Djokovic came into their own and started competing at the top of their game. Djokovic didn't succeed against peak Federer at Wimbledon the same Nadal did in the 2007 and 2008 championships. And Nadal did actually compete against the peak versions of both of his main rivals when he was also at or near the peak of his game. For example, Nadal's true grass peak is undeniably the second half of the 2000s which overlaps with Federer's peak there. The same can be said of 2011, where Nadal had to face the arguably best version of Djokovic ever.
3. Nadal has had short periods of extraordinary performance in his worst surfaces. His runs in 2008 on grass (Queens and Wimby) and 2013 in the Summer HC season (Cincinnatti, Canada, and the USO), for example, have nothing to envy the best of Federer and Djokovic. As a matter of fact, his triplet in 2013 is unmatched by either Fed or Djokovic, who are better HC players than Nadal overall. Nadal has also made great runs outside clay in other occasions, but those are the ones that stand above the rest. Although it is true that Djokovic has had great runs on clay, none of them approach those periods of dominance by Nadal on grass and HC.
4. Nadal has been thwarted the most by injuries. Djokovic now is a very close second, and Federer is not even close to bother mention. TBH, at this point Djokovic is so close in that area that it could be considered a negligible factor. Still, it's unfortunate to see in a player be bothered by injuries, specially when it prevents him from defending titles at his worst surfaces at the times when he was a favorite, as was the case for Nadal a few times in his career.
5. Nadal started winning slams the youngest of the three, and he has been YE #1 the oldest of the three. His consistency overall (not on his worst surfaces) is unquestionable.
Lastly, if you are not convinced...