At least once a decade, various naysayers are ready to call Time of Death on “Saturday Night Live,” lamenting that the show peaked during the early, Aykroyd/Belushi years, or started going downhill after Eddie Murphy left to become a movie star, or will never match the roaring madness of the Chris Farley era, or can’t even hope to equal the ensemble brilliance of the Bill Hader/Kristen Wiig/Amy Poehler/Fred Armisen/Maya Rudolph/Jason Sudeikis/Seth Meyers/Andy Samberg/Kenan Thompson cast, and so on and so on. Nevertheless, the show marches on, with the Sept. 28 premiere of Season 50 drawing the biggest premiere numbers since 2020 and ranking as the most-watched “SNL” episode ever on Peacock.

Over the years, “SNL” has become a well-oiled machine with the indefatigable Lorne Michaels at the controls — but it was born of chaos and seemed doomed to failure before it ever made the air. We are reminded of that in Jason Reitman’s kinetic and wickedly funny and unabashedly sentimental “Saturday Night,” which chronicles in near real-time the madness of the 90 minutes leading up to the show’s debut, which was “Live From New York!” on Oct. 11, 1975.

Reitman (who co-wrote the screenplay with Gil Kenan) delivers a stylized, “Birdman” meets Altman’s “Nashville” docudrama. The camera whips around, sometimes in dizzying fashion, taking us to the sets and dressing rooms and backstage hallways of Studio 8H as a 30-year-old Canadian named Lorne Michaels (Gab.