Mumford & Sons have achieved massive success, but they’re still desperate for respect. They’ve drawn from classic literature, sung with Bob Dylan, and reinvented their sound multiple times, and none of it seems to matter; as an old viral video once revealed, they will always be the band that sang the word “heart” 65 times in two albums. But on their third, 2015’s rock pivot Wilder Mind, they somehow wound up ahead of their time: They worked with producer James Ford years before Geese and gave Aaron Dessner his biggest credit up to that point as their associate producer. Critics and audiences alike were baffled, but it offered a new prototype for getting brooding,…