I agree with pretty much everything you said. It wasn't a horrible album by any means, I just thought it was weak by their standards.
I remember reading this interview with Alexisonfire before, and I think either George or Dallas of that band referred to how they didn't consider Green Day punk anymore, only it was in a non-inflammatory way and they said that Green Day were closer to being a U2-type band than a punk band these days, and it was about right.
Warning > Dookie > Insomniac > American Idiot > 1039 Smoothed Out Slappy Hours and other pre-Warner stuff > Shenanigans > Nimrod this is my opinion of course.