Most of the names he lists wrote songs I find annoying at best.

It goes without saying that you are in the deep minority, and when it comes to this subject there will always be a vocal minority.

I think his definition of a good song fails in being too universal, and his not finding great songwriters after the 90s corresponds to mass culture loosing out to smaller communities, so that we aren't all listening to the same songs and a particular sound doesn't define the times for everyone the way it did when you got whatever was on the radio or the shelves in the record store.

In large part, this is the rebuttal I would give. The best songwriters I can think of these days are from the Mountain Goats, Courtney Barnett, Gaslight Anthem, Okkervil River, Spoon etc etc etc (your list is different, thenewgreen's different yet again) -- I have no guarantee this guy has even heard their songs. However, even among my favorites I can recognize that history will remember none of them as all-time great songwriters.

Also, there is obviously still a shared culture of pop music, and the only person he mentions who fits into that demographic that I can recall is Lady Gaga (which read sort of like a sop anyway). There is still a fair bit of non-rap, non-indie, non-niche music that defines our "culture" nowadays.