I tend to agree. The sheer genius of it is it how it encapsulates British working life so perfectly, yet still remains extremely funny. It deserves to be considered amongst the all time comedy classics, but probably won't because of Ricky Gervais who annoys a lot of people, and most things he's done since have just reprised the David Brent role.
I massively disagree with your last sentence.
Brent is unique. I don't think gervais' other characters are anything like Brent, apart from in appearance obviously.
Regarding the rest of your post, I agree. But the thing I find most fascinating about the way it perfectly captures working life is that, as far as I know, neither Gervais or Merchant ever worked in that sort of environment. So find it amazing that they replicated it so well.
I think Gervais worked in various offices in his thirties before he was famous