Saturday Night Live has spent most of this year throwing its own 50th anniversary celebration, complete with legacy cameos, archival sketches, and a carefully curated special that stuffed every Hollywood A-lister it could find into the cramped, canary-yellow stadium seats of Studio 8H. But now that the sheen of nostalgia has faded, the show is back in the messier business of live comedy, which means it’s also back to not-so-quietly cycling out cast members and longtime writers in service of its own reinvention.