I've seen Mark Kermode about the place over the years and he's always seemed to me to be a fairly good thing: a passionate film enthusiast with an affable blokeish manner who dishes out serviceable commentary on new releases, and involves himself in what we must, per the modern idiom, call "the film community". But until reading this book I'd never actually read any of his film criticism – at least not knowingly – and it certainly came as a surprise to discover with what high regard he holds his profession, even if in respect of his own output he is annoyingly self-deprecating. Throughout Hatchet Job, Kermode keeps up a steady stream of asides of the kind my mother used to call "don't‑mind-little-me"; either because he is indeed ever-so-'umble, or – more likely – he's self-aware enough to feel the need to correct an innate arrogance. Either way, it's irritating, as are his cutesy anecdotes about the family dog, and his lexicon that draws heavily not on Americanisms per se, but on movie Americanisms – "doozey", "dopey", "kinda dopey" – that bespeak a lifetime spent in Soho preview theatres listening to execrable committee-penned dialogue.

Hatchet Job also contains some howlers: such as an Alanis Morissette-level misuse of "ironic" and all its cognates, and an "inchoate" for "incoherent" solecism that I found hard to square with Kermode's quarter-century hacking away at the typeface, and harder still to take given his view that film criticism can be a craft that in the right hands rises to the status of an art form. Ah, well, no need to worry, I'm not about to continue this hatchet job on Hatchet Job; after all, to write a book about film criticism is in the first place a little too much, but to critique such a work strikes me as altogether surplus to requirements.

But Kermode's book, as a sustained cry from the heart that over some 300 pages oddly modulates into melioristic mooing, is worth discussing. His anxiety that in the age of the internet and the worldwide web the role of the serious critic may be becoming otiose speaks to the contemporary condition. That he's unable to grasp the full extent of the change that's upon us cannot altogether be held against him; after all, very few people can look a wholesale social, cultural and psychological transformation taking place on an unparalleled scale steadily in the eye, especially if they're under a professional obligation to wear 3D spectacles a lot of the time.

Kermode certainly understands that change is afoot: he looks back over his own career, which began with manually typing copy and then delivering it to Time Out by public transport, with a certain nostalgia. He holds as integral to the business of proper criticism – and while he's talking about film this could certainly apply across all the arts – that its practitioners should be considered in their verdicts, be prepared to accept personal attribution, and should respect the production exigencies of their chosen art form. In the case of film this means observing embargoes and not "reviewing" work in progress. His mistake is to imagine that simply by transposing these diktats from the printed page on to the web the kind of culture he has commented on for so long can be preserved in virtual aspic. Kermode grasps, rightly, that the problem for contemporary writers of all stripes (film-makers and musicians as well), is that the fundamental link between words/images/sounds and money has been severed by the web; what he doesn't get is that this severing is irrevocable. He writes breezily about monetising web content, but really he's like a little Dutch boy with his finger stuck in a hole in the paywall, while over the top thunders a mighty inundation of free content.

The root of Kermode's confusion lies, I think, with another solecism. In discussing the demise of the film projector's profession he glosses a well‑worn media studies shibboleth thus: "when it comes to the inevitable change from analogue to digital, the medium is not the message – at least, not in its entirety." This is an observation Kermode wishes to extend to every aspect of the web revolution, but I somehow doubt that he's ever actually read Marshall McLuhan's Understanding Media; or, if he did, he simply cannot have understood it. McLuhan's point is that when it comes to the impact of new media on the human consciousness – both individual and collective – content is an irrelevance; we have to look not at what is on the screen, but how the screen is used. McLuhan saw in the early 1960s that all the brouhaha about what imagery was shown on television and what words were spoken was so much guff; the transformation from what he termed "the linear Gutenberg technology" to the "total field" one implied by the instantaneity of electricity was all that mattered, and this was a change in the human mind as well as the human hand. McLuhan's global village is indeed all about us now, and it already exhibits social, psychological and cultural behaviours that are entirely different from those implicit in the technologies of mass broadcast and individual, concentrated absorption.

Film is far more akin to the printed book than it is to the web page; and as for the criticism that accompanied it, this too owed its cultural traction to top-down and one-way technologies of dissemination. Kermode expends a lot of Hatchet Job on explaining that phenomena such as audience test screenings effecting change in movies are as old as the medium itself, while the auteur theory of film-making was always suspect and fragmentary. But what he wants to preserve against all comers is the work of narrative art as something that is given entire and unchangeable by its makers to its receivers. Unfortunately, like all Gutenberg minds, Kermode can only have an inchoate understanding of what's going on – but what he does get is that if film itself ceases to exist in its traditional form then film critics like him have their necks on the block.

And of course film has already changed a great deal: streaming is not analogous to the videocassette or DVD. Now we have instant access to an unparalleled library of films, books and recordings, we are wallowing about, really, in an atemporal zone of cultural production: none of us have the time – unless, like Kermode, we wish to spend the greater part of our adult life at it – to view all the films, read all the texts, and listen to all the music that we can access, wholly gratis and right away. Under such conditions the role of the critic becomes not to help us to discriminate between "better" and "worse" or "higher" and "lower" monetised cultural forms, but only to tell us if our precious time will be wasted – and for this task the group amateur mind is indeed far more effective than the unitary perception of an individual critic. In my working lifetime I've already seen the status accorded to book and film reviews undergo a tremendous decline – not, I hasten to add, because there aren't good reviews being written (this one is especially good), but because the media they are reviewing and the medium by which they themselves are delivered are both in a state of flux. All sorts of cultural production that was concerned with ordering and sorting – criticism, editing and librarianship – can now be seen for what it always really was: the adjunct of a particular media technology.

Kermode, himself an enthusiastic blogger, concedes that film criticism under the aegis of the web has become more a conversation than a series of declarations; what he can't bear to contemplate is that films also may become dialogic. Why not? For those who think that narrative art forms are in a state of crystalline stasis it's worth taking a slightly longer view: film is only just over a century old, the novel as we commonly understand it a mere two centuries old – the copyrights that protected them are about 150 years old. At the moment, the wholesale reconfiguration of art is only being retarded by demographics: the middle-aged possessors of Gutenberg minds remain in the majority in western societies, and so we struggle to impose our own linearity on a simultaneous medium to which it is quite alien. The young, who cannot read a text for more than a few minutes without texting, who rely on the web for both their love affairs and their memories of heartache, and who can sometimes find even cinema difficult to take unless it comes replete with electronic feedback loops, are not our future: we, the Gutenberg minds have no future, and our art forms and our criticism of those art forms will soon belong only to the academy and the museum. Bracing, isn't it, Mark?.