It’s hard to tell if the whole joke-band trend is going strong or getting tired. Blink-182 put down their tube-socks for good, Panic! at the Disco still haven’t gestated out of the niche ghetto, and Green Day are sitting back on their elder-statesman throne until the next campaign cycle. Fall Out Boy may not be the absolute last holdout of a dippy genre, but they certainly think they are, and their fourth release, “Infinity on High,” is a heartfelt yet desperate album that precariously straddles the line between artistic peak and bombastic burn-out.

What does it say about a disc when its best song has 17 words in the title, contractions and all? “I’m Like a Lawyer With the Way I’m Always Trying to Get You Off (Me & You)” truncates its relatively atonal verses en route to the tart-sweet chorus. Here, front man Patrick Stump shakes off the faux-funk style that grates throughout the rest of the album, especially on lead single “This Ain’t a Scene, It’s an Arms Race” (which had Adam Levine fans everywhere wondering how Maroon 5 did such a good F.O.B. impression). It may all be part of their great cosmic fuck-you to the establishment, but what kind of world do we live in if the lead singer of an emo-punk band doesn’t sound white (read: sexually frustrated)?

2005’s “Sugar, We’re Goin’ Down” was a breakout smash that toyed with the audience less than your standard joke-band hit, no matter how much we would’ve bent over and taken whatever hormone-induced contretemps songwriter Pete Wentz wanted to kvetch about. Thankfully, the lyrics were creative but controlled, something approximating poetry in this “Jackass”-dominated fart-meets-art genre. Everything would’ve been peachy if Wentz just wrote another 12 “Sugar”s for “Infinity on High,” but he ends up borrowing from everyone — Panic! on “Thnks fr th Mmrs,” Green Day on “Bang the Doldrums,” Jeff Buckley on “Hum Hallelujah” — except himself.

When he doesn’t borrow, he blusters, as on opening trio “Thriller,” “The Take Over, the Breaks Over,” and “This Ain’t a Scene,” where walking clichés like “The lies I weave are oh so intricate” trade lung-time with such head-scratchers as “At night we’re painting your trash gold while you sleep / Crashing not like hips or cars / No, more like parties.” We all knew F.O.B. songs were little more than Wentz’s charmingly oddball ego-dumps, but this is ridiculous.

To wit: “I’m a Lawyer,” a classic Wentzian composition that only took mega-star producer Babyface to make it sound like a great F.O.B. song. “Last year’s wishes are this year’s apologies,” Stump sings before launching into a deliciously catchy cycle of “Me and you / Sitting in a honeymoon / If I woke up next to you / If I woke up next to you.” Though it won’t lift Wentz’s romantic aspirations to drinking-age-level quite yet, “I’m a Lawyer” is pretty much the only song that validates his four-figure therapist bill.

But when Wentz pretends to fret about things greater than his rollercoaster libido or online nude-photo leak, he comes off as either treacly, limp or downright disingenuous, as on the quasi-religious piano ballad “Golden.” “And I saw God cry / In the reflection of my enemies / And all the lovers / With no time for me,” Stump sings, channeling his inner Billy Joe Armstrong on a song that resembles “Time of Your Life” about as much as Richard Cheese doing Celine Dion.

Used to be that Fall Out Boy just wanted to make people laugh, in that sad, overcooked, dog-walking-on-its-hind-legs kind of way. But as Wentz gropes in the dark for three-syllable words that rhyme with “sucker,” as Stump pimps out his once-endearing voice to the screeching soul-man style he should be eschewing, as the rest of the band play rhythm gymnastics on overproduced rock sludge, the askew humor that once extended beyond song titles gets shellacked in exchange for capital-m Music. Seriously, boys, that ain’t your scene.