you lost me at “separates them from infinitely shittier nu-folk peers like the Lumineers”.
sure, the Lumineers owe a lot of their success to Mumford and Sons, and rightfully so. But saying the Lumineers are shittier (In my opinion, they are better) or nu-folk (when I hear nu- in front of a genre I instantly think of Limp Biskit. I rest my case) is just weak and wrong. If you are in defense of Mumford and Sons, you have no right to lump the Lumineers into such a degrading category.

Also, as right as you are as to say Mumford owes their sound to Decemberists and Avett Bros., you totally just took the opportunity to shit on The Decemberists (who are obviously a better band) and to ignore the Avett Brothers (who are an even better band). The Avett Brothers, though they enjoy much success now and I’m not too crazy about their new sound, are the ancestors to Mumford and Sons and deserve so much more credit than they receive(d).

Mumford and Sons are a boring band and have way too much production to qualify themselves as a folk band. I’m sure each of the members are qualified musicians (though the singer’s voice has always annoyed me), but the collective sound doesn’t do it for me, personally. One only has to look at the Newport Folk Festival (and the folk scene as a whole) to hear what real folk is.