In these difficult times for business, perhaps we can learn something from the Wu-Tang Clan about the dangers of brand extension. Has any artist in history attained quite the degree of audience bafflement achieved by the New York hip-hop collective with their endless spin-offs and franchises and affiliations? You can find desperate, doomed attempts to make sense of it all online. There are discographies featuring a plethora of mysterious record labels that may or may not have been run by RZA and may or may not still exist. There are biographies of vaguely linked figures: "DJ WYO worked with members of Wu-Tang for many shows – he is best known for his look of confusion while trying to spin." And there are lists of innumerable affiliated rappers with amazing names: Shorty Shit Stain, Ill Knob ("aka Big Knob, aka Nibbly Knob"), and Ooh-Ahh Swordsman, the latter presumably a representative of the Wu-Tang Clan's little-known Somerset "fam".

Without wishing to lay the blame for the decline in the Wu-Tang Clan's standing at the door of Ill Knob, whose name suggests he has enough problems of his own, there seems little doubt the torrent of Wu-related output and accompanying issues of quality control has had a deleterious effect on public perceptions of the group. Nevertheless, there's no end to the brand confusion, as evidenced by Legendary Weapons, which apparently isn't a new album by the Wu-Tang Clan at all. You can see how the confusion arose, given that it is credited on the cover to Wu-Tang, was executive-produced by the RZA and features all of the band's core members except GZA. It's only the lack of the word Clan on the cover that might tell the buyer this is not what they are expecting. Whether GZA's absence or something more sinister accounts for Legendary Weapons' lack of official status is a hotly debated topic: one allegation was that its predecessor in the not-quite-a-Wu-Tang-Clan album canon, 2009's Chamber Music, consisted of vocals rescued from the cutting-room floor and stitched together over music by the Brooklyn soul band the Revelations.

Whatever its provenance, that album wasn't without its merits: while you got a lot of something one website calls "philosophical spoken word tracks by the RZA", which were every bit as spirit-sapping as that description suggests, it did include the spine-chilling closer NYC Crack, featuring the least likely Wu affiliate of all, Dutch vocalist Thea Van Seijen.

You could say the same thing about Legendary Weapons, even though it offers a less radical sonic agenda than Chamber Music's live band approach. Interpolating bits of 1993's Protect Ya Neck into the title track is a questionable idea at best: you can see why they wanted to draw comparisons with what you might call the pre-Ill Knob era, when incredible albums seemed to flow effortlessly from the Wu-Tang Clan's members, but it highlights the fact that there's not much that's genuinely new here. The producers to whom RZA relinquishes his place in the studio control room occasionally come up with something that's their own – the blasting horns of 225 Rounds are a highlight – but for the most part they're content to exist in the shadow of the music he made almost 20 years ago: lean, snapping beats, old soul samples, martial arts dialogue. It's not bad, but it's well-worn, utterly devoid of the jolt Wu-Tang once delivered listeners and the hip-hop scene alike.

The lyrics follow suit. Killah Hills, crack-dealing, 5 Percenter gibberish: it's nothing you haven't heard before, although it's worth noting that the old tricks still work, as evidenced by Method Man's dextrous turn on Diesel Fluid, which shifts from his love of the Smurfs to the inequities of the New York legal system in short order. Moreover, Legendary Weapons is still capable of delivering the odd surprise. Whoever digs up the dialogue from kung-fu films has excelled themselves on the opening of The Black Diamonds: "I warn you, shitface, I pick who I'm going to bury next." Inspecta Deck, lyrically hopeless on the last official Wu-Tang Clan album, 2007's 8 Diagrams, turns in a surprisingly fiery performance on Never Feel This Pain: his snarling defence of Barack Obama – "I'm proud of him, he real, just spent a couple million on the housing" – might be the best thing here. At the other extreme, Ghostface Killah is arguably Wu Tang's best lyricist, but he's upstaged on Meteor Hammer by the little-known Action Bronson, who rhymes "take your temperature anally and orally" with the deeply unexpected "make a batch of hummus, drizzle royally with oil", which if nothing else suggests a full and varied life.

It's possible the sound of Ghostface Killah being upstaged by an unknown rapper suggests he isn't really trying. Perhaps that's the problem with Legendary Weapons, which hints at the greatness of the Wu-Tang Clan but never really achieves it: another brand extension that makes you long for the real thing.