Brick walls and stone columns, even the grand ones of the Duke of York’s headquarters, do not a gallery make – and nor do limitless funds create a collector. The Saatchi Gallery, lavishly appointed but too often filled with trash, is rapidly becoming the white elephant of the King’s Road. Its new show, Abstract America, is yet more feeble than the lacklustre Middle East exhibition that preceded it. It confirms that Charles Saatchi’s global trinkets now offer neither meaning, interest, relevance or beauty to the contemporary art scene.

Three years ago, when Saatchi showed his collection of young American art in USA Today at the Royal Academy, I wrote that no one concerned with living art could afford not to look where he looked. That is no longer true. For this new survey, the plums of his American collection – the dark, post-punk installations of Terence Koh and Banks Violette; the exquisite neo-gothic drawings and weirdly formal mixed media sculptures of Mark Monahan – have been discarded, while works representing the weakest, dullest artists have doubled or tripled in number. With a single exception – the hard-edged cerebral canvases of Mark Grotjahn, which can be better seen at a solo show just opened at Gagosian – the painters here cannot paint, draw or compose. Sculptures look badly made and puerile. The advertised theme, abstraction in 21st-century America, has little bearing on the work – half of which is figurative – and lends no coherence to the display.

If anything unites these artists, it is that, like Saatchi, they are skilled at the niche marketing necessary to attract attention in a global marketplace. Each has an instantly recognisable trademark too simple to be developed, but capable of infinite repetition. Kristin Baker’s is fast cars, represented in geometric-futuristic fragments painted on PVC panels, giving an ultra-sleek, freeze-frame effect. Aaron Young’s in “Greeting Card” are motorbikes – he has them driven across his painted plywood surfaces, so that the impact of the tyres burns into them “spontaneous scribbles and gestures associated with Pollock’s subconscious negotiation of the canvas”. Elizabeth Neel’s are dogs – sketched fighting (“Good vs Evil”) or copulating (“The Humpndump”) in cartoon style, then overpainted in sarcastic rosy hues. Bart Exposito’s are the flat doodles of graphic design, suggesting corporate logos but derived from 1960s minimalism, and offering, according to the catalogue, “the Zen-like fizz of commodified nothingness”.

Everything is big – mockingly too big for the empty subjects – and desperately retro. Sources tend to be photographs or computer manipulations; of original transformation there is none. The catalogue claims that these “artists’ alter egos may well be the DJ. The brushstroke has been replaced by the ‘riff’. This is the age of ‘remix’. Raw material is downloaded. Photoshop is the tool. These knowing abstract practictioners have irony at their disposal and can switch to tie-dye aesthetics or psychedelia as fast as they can quote Malevich or Brice Marden.” This is an excuse for tired, derivative painting repackaged by advertising talk into 21st-century cliché.

Sculptures are as vainglorious and vapid. Agathe Snow’s flaccid triptych of figures constructed in cloth and wood, dripping balloons, shopping bags, McDonald’s flags, party hats and other commercial debris, looped over graffitied crucifixes, opens the show. Stephen Rhodes’ green and black rubber box, from which protrudes the head and tail of a serpent, is titled “Ssspecific Object” in reference to Donald Judd. Matt Johnson’s “Malus Sieversii” is a wooden apple, flesh mostly gnawed, its remains carved into a winding staircase. Ludicrously, these affect to tell a narrative evoking art’s oldest subjects, man’s spiritual journey from Eden to Golgotha.

Saatchi is a private collector who can, of course, indulge his own taste, and charges no one – the Saatchi Gallery is free – for sharing it. His King’s Road premises are also a showcase for his online venture, the Saatchi Gallery website, which has powerful effects on art, art-making, the art market, collectors and audiences. By encouraging art to be bought and sold online, and by funding countless competitions to transform young, undeveloped talents into fool’s gold, Saatchi is turning art into a virtual encounter rather than the imaginative, transcendent, lived aesthetic experience it has always been. This is a loss that strikes not only at the heart of how we respond to art, but influences its making. Impressionable, broke young artists cannot help noticing that if an instantly seen, niche-marketed, reproduced image is what sells a name, the actual presence of an artwork, the subtlety and many-layered interest that connoisseurs cherish, becomes less important. I think this is what Saatchi means by “abstract” – abstracting art into non-existence so that a work becomes just a marketable commodity. Art cannot be made that way, and this show is a terrible warning of what happens when its practitioners try to do so.

‘Abstract America’, Saatchi Gallery, London SW3, to September 13