Almost as an aftershock from that gigantic finish to the Marvel Cinematic Universe saga that was Avengers: Endgame, the X-Men series now comes to its own weirdly anticlimactic end. Or maybe it’s truer to say that the prequel series showing the mutants’ younger selves – with James McAvoy rather than Patrick Stewart as Xavier, and Michael Fassbender rather than Ian McKellen as Magneto – has now circled in on itself as far as it can. There is no place to go other than forward to the present day, where we came in.

X-Men: First Class (2011) started us in the 1960s, X-Men: Days of Future Past (2014) took us to a mind-bendingly alternative 1970s and X-Men: Apocalypse (2016) found the mutants in the 1980s with glimpses of Ronald Reagan and William Buckley. Now we are in the early 90s, and Raven (Jennifer Lawrence) is pointing out the misogyny of the gang’s title: the female mutants are saving everyone’s asses – maybe they should be called the X-Women.

At the centre of this movie is young Jean Grey, played by Sophie Turner (Sansa Stark from Game of Thrones). Grey’s destiny is the drama’s driving force, although this does potentially raise a strange question. It is no spoiler to point to the existing X-Men movies, in which the older Jean Grey is played by Famke Janssen (who has called out industry sexism after hearing no offer to reprise her role in cameo, unlike McKellen and Stewart), which means the audience is already aware of how her story ends.

But the point here is to show how Jean Grey’s story starts. Writer-director Simon Kinberg shows a very young Grey (played by Summer Fontana) riding in the back of the car with her mom Elaine (Hannah Anderson) and dad John (Scott Shepherd). Her disturbed, unfocused powers lead to calamity and soon Jean is being brought up as a mutant prodigy by Dr Xavier (McAvoy). Later, in the 90s, the X-Men have to make a special mission to rescue Nasa Challenger astronauts from some strange deep-space eruption; Jean Grey almost dies in the attempt but survives, infected by an evil cosmic force. She is now Dark Phoenix.

The most interesting aspect of this film is McAvoy’s Xavier. He is more opaque, more worldly, more secretive – and drinking more heavily. For the first time, we realise that he is not the idealist that we might have imagined. Raven is increasingly angry at Xavier’s recklessness and egotism, risking his pupils’ lives for his own glory – maybe as a result of being too close to the Washington political establishment.

There is a surprise in store for Jean, though due to the superhero-style weightlessness of the film’s events, this surprise doesn’t pack the psychological punch that it should. Fundamentally, we are heading for the same good-versus-evil showdown that closes out Marvel movies, with lots of digital effects. The battle here is certainly spirited, and Jessica Chastain looks intimidating as the alien Vuk – although the role is a waste of her talents. Magneto’s reappearance is sub-par, and so, frankly, is Michael Fassbender’s performance, although his character has been starved of the kind of interest devoted to his old rival Xavier. We are also denied a bullet-time setpiece sequence for Quicksilver (Evan Peters), which were witty features of previous instalments.

The point of a phoenix, dark or otherwise, is that it rises from the flames. But these are the flames in which this franchise has finally gone down.

• This article was amended on 5 June 2019 because an earlier version misnamed the character of Jean Grey as Jane on some occasions. This has been corrected.