Don't think that necessarily means a weak era. If Ferrer was the 4th best player on tour, then it'd be the weakest era of all-time for sure, I wouldn't even watch tennis if the sport had such a dire lack of talent.
But everyone knows that's not the case, he's not even among the 10 best players. His seed is a result of abusing the flawed ranking system to no end, like Boredo once did to get his high seedings. There are bound to be mugs getting top 5 seeds in any era, strong or weak, as long as the current ranking system isn't changed to prevent this kind of abuse, it says nothing about the strength of the era.
blah blah blah, Ferrer has more top 10 wins than Berdych, suckit.
And as for tennis merely requiring fitness rather than talent to succeed nowadays, why doesn't some elite triathlete simply pick up a tennis racket and start dominating the slams in that case?