“It’s hard to believe you were ever young!” quips a spritely Turkish Assassin after Ezio Auditore has informed him he learned a few lute chords in his formative years. The Ezio of Assassin’s Creed: Revelations is older and wiser. His beard is flecked with grey, and old scars give his wrinkled face an asymmetrical handsomeness.

It’s also a joke designed to break the fourth wall: fans of the series have known Ezio his whole life. We first met the next Master Assassin when he was a kind of stand-in for Casanova, a young Florentine who applied his latent talents for climbing and stealth to the singular goal of gaining access to girls’ bedrooms – no surprises he also made hamfisted attempts at courtship that included lute-fuelled serenades.

But extrapolate further and the line works on a final, unintended level: it might as well sum up the sentiment Assassin’s Creed: Revelations leaves players with. If the years sit heavily on Ezio, they’re sitting equally heavily on the franchise he’s spent his life fronting.

Make no mistake, it’s very easy to be critical of Assassin’s Creed: Revelations. Its flaws are only more apparent because they're juxtaposed against such robust core gameplay. Each instalment in the series has exceeded the high expectations asked of it, and none more so than last year’s Brotherhood. Revelations also ensures that Assassin’s Creed remains the most accessible stealth action game on shelves today – what the series has done well in the past it continues to do sublimely here. Ezio traverses terracotta-tiled rooftops, descends into the crowd, closes on his target and slips his blade underneath a ribcage leaving only gasping confusion in his wake.

Considered in isolation Revelations is a very strong game, but placed amongst its forebears and with an eye to the future, it appears to keep the series in a holding pattern. Nothing demonstrates this more ably than the lack of newly engaging narrative advancements.

We rejoin Ezio some years after the events of Brotherhood as he seeks knowledge locked away by the Crusades-era Assassin Altair beneath the former guild stronghold at Masyaf. His search for keys to unlock this library takes him to Constantinople in the years immediately following the Ottoman Empire’s usurpation of the Byzantine. Predictably, the Templars are on the same path and so the stage is set for another cloak and dagger showdown in the alleyways and courts of another old world capital.

As ever, these missions are punctuated by the now-wearisome presence of Desmond, our contemporary conduit to bygone Assassins via the sci-fi miracle of “DNA memory”. In the past, players have grudgingly been able to accept the mewling Desmond as a necessary narrative keystone, a character that links together what once promised to be a pantheon of leading Assassins scattered over the centuries. As it turns out, he’s been the link between two characters only: the largely jettisoned Altair of the original game, and three full instalments of Ezio.

While Altair makes sporadic cameos as a playable character in Revelations, the game employs a convoluted “memory within a memory” plot device to do so. The keys Ezio uncovers contain Altair’s memories. As such, Desmond is only necessary for us to see these sequences insofar as he gives us access to Ezio’s “memories” of Altair. Desmond’s enhanced role in Revelations, then, is doubly frustrating.

The Altair missions themselves are ably constructed but by and large lack any real purpose beyond the occasional diversion from the game’s main thrust. But Altair isn’t the only content now forcing Assassin's Creed to leave the top button of its jeans undone. Hand grenade crafting is not only antithetical to the very concept of the silent killer, the needless feature is so prolific in the game world as to be ridiculous. The Ottoman and Byzantine guards, and the henchmen that fill the ranks of the Templars all carry the wildly various base components of bombs in their pockets like so much lint. There must surely be more bomb crafting stations in Ubisoft’s vision of Ottoman Constantinople than there are doctors.

Bombs are joined by the hookblade and the zipline. Liberally scattered throughout Constantinople these are glorified flying foxes that have no contextual relevance whatsoever beyond allowing a supposedly secret society to negotiate the city in high profile as if it were a dolled up obstacle course – which, of course, Revelations’ Constantinople really is.

Indeed where Brotherhood innovated by focusing on one city and creating an Assassins Guild system that added depth and vitality to the experience, Revelations’ new additions are either superfluous or poorly executed.

Nothing better describes this than the Assassin’s Den defence mini-game. When the Templars become aware of too much Assassin activity in Constantinople, they’ll launch an assault on one of the dens that gives the guild economic control over one of the city’s districts. It’s left to Ezio to order the den’s defence. He must spend morale points, gained through success, to place further defences and assassins in order to stave off increasingly powerful waves of Templar attacks. It’s promising on paper but its execution is limited, reducing it to little more than a frustrating penalty for failing to bribe heralds or dispatch officials.

Reviewing the additions, the impression we’re left with is that they've been included to meet a mandated quota for back-of-box “new features” in what has become Ubisoft’s annual franchise, rather than resulting from any great insight as to how the Assassin’s Creed experience might be improved. The wider concern then is that Ubisoft may have finally run out of good new ideas while already assuring the public that another instalment will be delivered before December next year.

It cannot be said enough that underneath all the padding remains that same excellent stealth assassination gameplay. Brotherhood's multiplayer returns largely unharried, and fans enamoured with the series will certainly be able to see through the surplus soft tissue to appreciate the singleplayer's unquestionable inner beauty. The rest will rightly conclude that Assassin’s Creed: Revelations is the most disappointing entry in a spectacular series.