I wouldn’t commend the way that Mumford & Sons have distilled what the Decemberists have done. In fact, I would regard Mumford with even more disdain for this. I don’t understand why this article uses such an example as a point of praise for the band. They took another band’s sound and subject matter, removed the quirk and replaced it with ‘cooler’ vocals, and made the lyrics less interesting. This doesn’t sound like a good band to me.
A good article and an issue that has occurred to me in recent months. I started noticing this indie folk/top 40 crossover during the summer. I think you could have mentioned Of Monsters and Men as another example of a ‘Mumfordized’ band.