If Soulja Boy’s release of the 50/13 mixtape is a precursor to the Promise album, then many of his longtime fans may end up disappointed. Clocking in at 15 tracks, the tape is a smorgasbord of lazy production, uninspired lyrics, off-beat flows, and skippable tracks. It feels like he decided to make this over some holiday downtime, because it certainly sounds like it didn’t take much time and effort to produce, and he would have been better served focusing his attention on his next album. Soulja Boy would benefit from the less-is-more approach on his tracks (and releases of his mixtapes, ...