I've said it many times, but I'll pad out my post count with it again: Edge is the problem with modern U2. Bono's increasingly obtuse lyricism is "a" problem, but Edge has always guided the musical direction of the band with his brilliant, experimental guitar work, and now he is neither brilliant nor does he experiment with his guitar. It's the same old shit all the time. No curveballs, no surprises. The bar has been lowered to the point where the solo on The Troubles is considered a major highlight.
His tone was so miraculous back in the day that a few careful strums of distorted guitar could change the tenor of songs like WGRYWH, which is effectively a catchy pop song that he darkens several shades. However you may feel about The Playboy Mansion, Edge's wah pedal work adds a necessary layer of sleaze, whereas his slide work creates a heavenly counterpoint to the song's carnality. The colorful sound manipulation of Lemon and SDABTO took those songs in a psychedelic direction that didn't feel forced; it was a natural progression from his unbridled playfulness in the studio.
Songcraft is important, but lots of decent, passable musicians write good songs. They're not all that hard to find. A studio alchemist that can transform a few notes into a dazzling waterfall is very rare. Alas, lately we've settled for chunky power chords and tributes to his old solos. Until Edge feels the urge to take his guitar work somewhere special, the band will remain stuck in neutral.