I don't think this era is weak or neither super strong. Just before Nadal came up, there were a few clay court specialists around albeit at the latter end of their career. But Nadal proved to be too good and distanced himself from others by miles, even Federer who is a pretty good clay court player. He started sweeping the clay tournaments and no one else could stand up to the standard until 2011 Djokovic. In fact, regardless of court type, other than Del potro currently there's nobody who can regularly threaten against the top players. And being a very aggressive player, Del potro does not get help in clay courts. Murray is a bit curious case as he grew up training in Barcelona and given his relatively defensive style last couple years, he should have at least got to the semis or finals of the clay tournaments.
Regarding the domination period of Federer, that was not an weak era either. During that time, at least four of his opponents were slam winners and multiple slam finalists (excluding Agassi). But again, Federer proved to be too good to stand up against. The players who could at least sometimes challenge to match him were either too inconsistent or injured (Safin, Hewitt, Nalbandian).
Frankly, I'm afraid that the true weak era might come next when Djokovic, Nadal etc retires unless some young guns steps up to a few more levels.
To answer your 2nd question, yes - there's a lot of arguing and disagreement among the people who work in Science. But they usually have some rational points to back up their opinions. And most of them are not hellbent on standing on their points when they understand the other persons' reasoning.
Cheers