I can't claim to be a religious follower of superhero movies. And I'm certainly not a comic-book aficionado. But I've seen most, if not all, of the recent Marvel X-Men and Avengers sagas. Given all the subtitles and sub-series of the X-Menmovies and their long run, unless you're a devotee, it's hard to keep up with them, especially as they jump backwards and forwards in time and periodically recast.
But the basics are that mutants with special powers in an uneasy relationship with humans who don't know whether to fear the X-Men (there are women, too) or enjoy the benefit of the help they provide in order to prove their bona fides. The X-Men, under the care and guidance of Dr Charles Xavier, have their own HQ (a school for the young of their kind) but one of their number, Magneto, has been a rebellious thorn in the side until recently.
There have been readings of outsider subtexts - Magneto in the comics was eventually revealed to be Jewish - and the various characters, most with both "normal" and superhero names, bicker and joke and cooperate and otherwise act like a family. The series has had its ups and downs but has been far superior to the various attempts to film another superhero group, The Fantastic Four (I wonder why: the latter has only four distinct characters to deal with compared to the many X-folk).
In this film, telekinetic and psychic Jean Grey (Sophie Turner) aka Phoenix, who has been raised and mentored by Xavier since surviving a car crash with her parents, is the main focus. As an adult, she is part of a space rescue mission and is hit by what appears to be a solar flare. In fact, it's a destructive force that has some strange effects on Jean, including the recovery of some disturbing memories, and it seems she has succumbed to the forces of darkness, encouraged by a mysterious shapeshifting alien named Vuk (Jessica Chastain, looking like she's had a bad facelift), leader of the D'Bari. The other X-Men are divided on how to handle the situation and the self-exiled Magneto, who has his own mutant refuge, rejoins the fold to help.
X-Men: Dark Phoenix is the 12th, and apparently the last, in its particular series (at least before the inevitable reboot, scheduled for next year). It's a bit of an anticlimax, and not just because Hugh Jackman's Wolverine is no longer present (or even, as far as I could tell, mentioned).
The film is lacking the humour and warmth that were highlights of the earlier movies and the betrayals and explorations of motive that are key to the story don't resonate like they should. The shapeshifting extraterrestrial villains who come to Earth are fairly menacing but not terribly interesting or well explained. And the moral issues don't really inspire any sense of urgency or ambivalence.
There are a couple of decent action sequences - the space rescue and a big train battle - and a gamechanging event or two, and some of the characters get a moment or two to shine, but overall this is a bit of a disappointing conclusion.
And don't bother waiting through the credits unless, like me, you like checking things like the cast and songs. There are no extra scenes as a reward for sitting through the hundreds of names. One thing I did learn: some of the special effects were done in Australia.