The only thing surprising about Mariah Carey’s residency in Las Vegas is that it didn’t start at an earlier point in the post-millennial extended-run boomlet, which was kicked off by Céline Dion back in 2003 and which had, before “#1 to Infinity” was announced in 2015, included retrospective shows by the likes of Britney Spears, Shania Twain, and Rod Stewart. One of pop’s premier divas skipping tour and beckoning her fans to come to her? Of course, dahling. Arranging the show so that it focused on her 18 chart-topping singles, an achievement that’s a rallying cry for her Lambs? [Whistle note here.]Mariah’s series of shows at the Colosseum in Caesars—the same theatre where Celine embarked on her extended run all those years ago—wrapped up last week. I caught one of the final performances, where she preened and belted through her biggest hits (and a couple of other notable tracks) while well-appointed dancers who could have been lured over from the Rio’s Chippendales revival flowed around her. James “Big Jim” Wright, a Flyte Tyme Studios alum who’s worked with Mariah since the Rainbow era, was the music director and, at times, the star’s soothsayer; Trey Lorenz, who became an MTV fixture when Mariah’s MTV Unplugged cover of the Jackson 5’s “I’ll Be There” hit big, sang backup. During longer set changes, a DJ would come out and try to hype up the crowd while running through megamixes of Mariah songs that had been hits, but not chart-toppers—hello “Can’t Let Go,” hi there, “Obsessed.” (Sadly, “All I Want For Christmas Is You” was missing, but Mariah’s holiday Vegas residency, set for Caesars this December, will no doubt rectify that.)A Mariah Carey show in 2017 not only gives one a chance to see her sing while sporting a fuzzy purple bathrobe that resembles an overly huggy Muppet; it doubles as a tour through pop’s last quarter-century. When she started out, Mariah was presented as a diva in the Whitney mold, a Long Island-born glass-breaker whose ability to leap octaves in a single bound was often the guiding force behind her songs’ arcs. “Vision of Love” and “I Don’t Wanna Cry” (produced by glitter-master Narada Michael Walden on record) updated the torch song for the MTV era, which was easier to get away with in the era when pop gave women more leeway about acting (and being) older; “Someday” and “Dreamlover” bubble and fizz, allowing for ample room to embark on gravity-defying vocal runs. “Fantasy” is a caesura for Carey’s career, its “Genius of Love” sample lending her a lighter-than-air platform off which she could vault and giving a shot of somewhat recent history to pop radio; its remix upped the Tom Tom Club quotient and dropped Ol’ Dirty Bastard into the mix for good measure.In the immediate wake of “Fantasy,” Mariah kept her big ballad quotient high (the chart-dominating Boyz II Men duet “One Sweet Day,” the diva showdown with Whitney Houston on “When You Believe”) but the taste of youth-culture fame that song had provided resulted in the production of varying clones, each with different old-school samples that suspiciously echoed “Genius,” each with different MCs serving as Mariah’s foil. It worked for a while, and the template laid down by these songs—gossamer vocals from singers bedeviled by dudes who were either lusty or self-obsessed, or both—calcified into an R&B norm. The Emancipation of Mimi—Mariah’s 2005 rebound from a rocky early-naughts period that included the megaflop Glitter and her multi-album contract with Virgin Records being canceled—broke the mold once again, allowing Mariah to show off her subtlety on songs like the gently tut-tutting “Shake It Off” and the passionate “We Belong Together.” While she was still flaunting her vocal prowess, she also reined it in at crucial moments, allowing the bruised emotions to take centerstage.Since then, Mariah has released a clutch of quality singles that have given space to her slightly maturing voice, which can still soar but which also has a bit more body in its low end, sounding a bit similar to the huskier affectations of Christina Aguilera. However, the tribulations of the music business—and those faced by female R&B artists in particular—have, sometimes unfairly, aced her out of the mainstream. “H.A.T.E.U.,” from 2009’s tumultuous Memoirs of an Imperfect Angel, got notice when it was remixed with Ghost Town DJs’ 1996 rollerskating jam “My Boo,” but received little pickup on radio. “#Beautiful,” her 2013 collaboration with the ever-omnivorous Miguel, was absolute candy, its simple guitar lick and swaggering beat seemingly adding up to a lock for song of the summer. That didn’t quite work out. (“Blurred Lines” hogged the headlines; “Get Lucky” got the nerds excited.)The setlist for Mariah’s Vegas show, as a result, halted at 2008; even the gangster-era throwback YG, who appears on her latest single “I Don’t,” was relegated to sitting on the bed that serves as a set piece during “Touch My Body,” Mariah’s most recent chart-topper. (That was one of two beds involved in the evening’s festivities, both of which were motorized so that she could enter while seated. Other modes of on-stage transportation included a jet ski, a motorbike, and a pink Cadillac a la Christie Brinkley’s big entrance in Billy Joel’s absurd video for “Keeping The Faith.” When a diva is given the choice between wearing arch-contorting heels and walking on stage like a common person, there’s only one real option.) It was mostly fine, with Mariah dipping into the audience to say hi to her lambs a couple of times; why anyone wants her to perform choreographed steps, especially given her choice of footwear, is odd. And besides, she was always more of a bop-along type, as her early videos show.While the retro bent of the show was in keeping with Vegas traditions, it was also a moment to wonder what might need to change in order to allow the pop world to allow women over 30 back into whatever mainstream exists in 2017. A splintering of the Hot AC format—so that one type of station explicitly caters to, and even at times programs new music by, grown women—might seem like a desperate solution, but it’s one that would have at least allowed “#Beautiful” and other recent, and more than decent, songs by Carey’s peers and immediate heirs to get a little shine.