If you think about it, it must kind of suck to be a massively successful band with a decades-long career. See, when a band achieves a high level of acclaim built on a beloved signature sound, they are pretty much bound to it forever. If the band makes a record that in some way defies expectations, they risk alienating their buying public. However if the band doesn't alter its sound enough, they risk being considered stale or boring or repetitive. Basically, the band becomes its own competition. U2 has been struggling against itself for years, basically since the commercial and critical success of The Joshua Tree in 1987. By that time they'd already crafted a signature sound (chugging rhythm, open, ringing guitar, passionate vocals, and soul-searching lyrics), but songs like With Or Without You and Where the Streets Have No Name cemented it in our hearts and minds forever. Since then, any U2 product that hasn't sounded pretty much exactly like those songs has been branded...
To be read at maximum volume.