Jimmy Eat World has never been the most complex band, or the hippest, or biggest-selling. Its jangle-pop sound isn’t timeless, or particularly influential. Its output since 2001’s “Bleed American” and its feel-good mega-hit “The Middle” has been a bit, well, middle-of-the-road.

Yet the almost-full room Monday at Seattle’s jumbo-sized Showbox SoDo proved that while the Mesa, Arizona foursome’s commercial peak might have passed, they’re far from forgotten.

Singer-guitarist Jim Adkins, guitarist Tom Linton, bassist Rick Burch and drummer Zach Lind kicked off their hour-plus set in fine form. Opener “I Will Steal You Back,” from the recent “Damage,” and cantankerous anti-music industry screed “Your New Aesthetic,” off 1999 breakthrough “Clarity,” showcased the sensitive-guy harmonies and alternately caustic, twinkly guitar interplay that registered the group on critics’ — and Billboard’s — radars back in the late ‘90s.

Despite sounding dubious on paper, its hard-rocking rendition of Taylor Swift’s pop-country chart-topper “We Are Never Ever Getting Back Together” fit surprisingly well alongside “Damage’s” adult-contemporary breakup songs.

The show lost some traction in its second act. When Adkins swapped out his cherry-red, semi-hollow-body Telecaster for an acoustic guitar, it signaled a transition into weepy balladry — never Jimmy’s strongest suit, hard as they try. Even after the band plugged back in, the monosyllabic “Kill,” “Work” and “Pain” — all from 2004’s “Futures” — came up short in the hook department, and the audience’s enthusiasm began to wane.

Eventually, however, they regained momentum, first with 2010’s AM Gold-styled “Coffee and Cigarettes” — featuring guest vocals from Courtney Marie Andrews, a Phoenix-born, Seattle-based singer-songwriter — then, a series of throwbacks for their longtime fans, now mostly in their thirties.

Though pushing 40 themselves, Adkins, Linton, Burch and Lind sounded years younger during the set’s kinetic final salvo, a blistering succession of tracks that included reggae-tinged singalongs (“Sweetness,” off “Bleed American”) and tense slowcore (“Goodbye Sky Harbor,” from “Clarity”).

By the time “The Middle” inevitably rolled around, Adkins — who, since the group’s early days, has been known to arrive onstage drenched in sweat before even playing a note — was wet-haired and red-faced, but grinning from ear-to-ear. Throughout the night, his bandmates — while less demonstrative — showed their catalog to be deeper than casual listeners usually give it credit.

At its best, the deliberately-paced opening performance by Ithaca, New York synth-rockers X Ambassadors echoed the narcotic melancholy of vintage Depeche Mode; at its worst, the saccharine modern top-40 of The Fray.