A ridiculous CGI half man half shark creature rips a human being literally in half in gleeful slow motion, but we cut away from a sex scene. Welcome to American commercial cinema.

Back when I was a professional, paid critics for several magazines this is the exact type of movie I described using metaphors about the sugar in the giant soft drink or the salt in the popcorn butter you get at the cinema being delivered to your system all at once – something that's not particularly good for you to begin with (however enjoyable) and pumping you so full of it you quickly feel the ill effects of ingesting too much.

For all the extreme nature of the 'grown up' elements (blood, violence swearing) in this film, it's a dreadfully drab, corporate, big studio, three act superhero mash you've seen a million times, writer/director James Gunn using a cudgel while dressed as a studio suit to try to stand out. The 'extreme' content is all individual scenes and shots. The story, character tropes, staging and even the camerawork is nothing you haven't seen done better elsewhere.

In creative intent as well as a plot device, the old Suicide Squad is no more. Instead, the government spook who oversees the program, Amanda Waller (Viola Davis) seems to recruit and despatch multiple teams of violent or colourful ex cons with explosives in their heads she'll detonate if they go off-mission.

We see one such squad land on the beach of the fictional island of Corto Maltese (and I hadn't realised this was a real place in the DC universe – last I heard it mentioned was way back in Tim Burton's Batman, when Kim Basinger as news photographer Vicki Vale had Corto Maltese war photography in her portfolio) and all die in short order when the Corto Maltese army meets them.

But there's another, alternate team elsewhere on the beach that penetrates the coastline and makes for their rendezvous point. The only original pair are Harley (Margot Robbie) and soldier Flagg (Joel Kinnaman). Will Smith, smartly steering clear as Deadshot, is replaced by Idris Elba as... Bloodshot. Yes, it's that lazy. I haven't seen dumber writing since Terminator: Dark Fate introduced us to the AI supercomputer Legion, a plot device exactly the same as Skynet but, you know, different.

John Cena is also on hand as some sort of ultra-patriotic supersoldier who wears a tin can on his head, which even the movie itself at least has the grace to make fun of, and there's another guy with a onesie covered in polka dots who can get them to come to life and attack his enemies... or something. If there were any others, I cared so little I've already forgotten them.

Their mission is to depose the aberrant Corto Maltese government, a new, anti-American regime that's overthrown the previous one, and when they discover it's aided by a scientist who's created a starfish the size of a skyscraper in a top secret facility, the squad realises the new government has a plan to unleash the monster and take over the world... or something.

Instead, like a hundred other Jurassic Park clones, it gets out and starts to lay waste the city around it, the heroes conveniently on hand to save the family-oriented, simple life-worshipping South Americans (wonder which executive took note of the spectacular growth in the Hispanic demographic in domestic moviegoing and mandated that).

Look, I know I sound cynical, but as an avowed moviegoer, I'm constantly aware of Sturgeon's Law, and this falls right into it. Plus, superhero movies always have an inherent limitation in that the stupid characters/names/powers are perfectly at home on a page of comic book panels – trying to situate them in any kind of real world just reminds you of how dumb they sound and look.

When taken to such an extreme like it is here with the ridiculous shark monster thing and Peter Capaldi's stupid-looking oversized brain prosthetic, I just couldn't buy into anything else that was going on.

And no matter how many press narratives about James Gunn being off the leash they push, you can also see the fingerprints of panicked Warner Bros executives all over it, remembering how badly received the 2016 original was. It's a lurid, needlessly frenetic, ugly, technicoloured shit pile you'd throw your shoe away if you stepped in.

Last but not least, I feel sorry for poor Sonia Braga, who was the emotional backbone of Fernando Meirelles' blistering City of God back in 2002 and hasn't been able to land a role in a decent project ever since. She's giving it her all here, believing every word as a revolutionary rebel soldier, but she's the only one who cares.