Sitting in the darkness of the cinema, watching Joker: Folie a Deux, it was hard not to be swept up in the film’s complex and challenging themes, the truly haunting soundtrack and the genuinely stunning performances from the film’s two leads, Joaquin Phoenix and Lady Gaga.

Cut from the cloth of DC Comics and set in Batman’s Gotham City, this was a comic-book film so good that it basically broke the box. For all of its perceived faults, and dark, fantastical touches, director Todd Phillips created a universe so plausibly bleak that the only thing it could never have stood was the arrival of a character as ridiculous, in this context, as Batman himself.

In the cold, hard light of day, however, Joker: Folie a Deux was torn to shreds by film critics and then abandoned by audiences in response, who took the collective huff-and-puff from the cinematic cognoscenti’s answer to the big bad wolf as irrevocable confirmation that the film was not worth seeing.

What a terrible, terrible loss. And what a collective waste of breath from a class of thinkers who ought to understand there is more to movies than popularity and adherence to comic-book canon. It wasn’t Joker enough? It was too Joker? Who is to know? And who, in the end, decides what is art, and whether art is good?

So busy were the critics in their pursuit of a wry line – “a folly that rings hollow”, “a bad joke” … on it went – that they forgot their civic duty was to illuminate the nuance of cinema, not put it to the egotistical torch.

Here’s what you missed: Joker: Folie a Deux is a masterpiece. Not a once-in-a-generation masterpiece but an ambitious and emotionally intelligent film that challenges everything it touches, including, it seems, the fragile sensibilities of the world’s film critics.

These critics are, after all, the same people who told us that Casablanca was “horribly wooden” and filled with “cliches everywhere that lower the tension”. That The Wizard of Oz had a light touch of fantasy that “weighs like a pound of fruitcake soaking wet” and thatVertigo was “another Hitchcock-and-bull story in which the mystery is not so much who done it as who cares”. (That was Time magazine, by the way.)

Star Wars, the film that generations of moviegoers (and many filmmakers) see as a cinematic North Star? “It’s an assemblage of spare parts. It has no emotional grip … an epic without a dream,” wrote Pauline Kael – arguably one of the finest film critics of all time – in The New Yorker, no less. Critics. What are they good for, anyway?