WTF, Luc Besson? WTF?
The title sequence is promising.
It only gets worse from here.
Valerian and Laureline's introduction is full of clumsy "as you know" dialogue. When they enter the city they both live in, we get an even clumsier piece of exposition as the computer tells them everything about that city. It's supposed to house thousands of species, but very few of them are utilized in the movie (I'll get to them in a moment).
Speaking of the two main characters... They're just not very interesting. Dane DeHaan is terribly miscast; he looks like a strung-out junkie, not a badass space agent. Cara Delevingne isn't any more compelling. These characters needed charismatic actors with chemistry between them.
Rihanna seemed somewhat likable as the PG-13-rated erotic dancer just because she's an abused refugee, but her only role is to serve Valerian and then be killed off, which evokes the stereotype of a disposable sex worker.
Members of the alien race that abducted Laureline are just as disposable and just as stereotypical. Apparently they're less intelligent than human and have a primitive tribal society, so they can be killed like insects - a very unfortunate throwback to the European colonial attitude that will offend any Trekkie's humanitarian ("touchy-feely", as Uncle Trey once put it ) sensibility. They're treated worse than the Gungans in TPM. This might've been an intentional reference to old sci-fi/fantasy (the original comic book is 50 years old), but it just doesn't play very well in 2017.
Just like Avatar, Valerian felt like a passion project that the director had in mind for decades and, when finally given the chance to film it, couldn't bring himself to kill his darlings. What we got is a badly constructed plot with amazing eye candy. A writer with less attachment to the source material could've probably delivered a tight script instead of this mess, but, just like George Lucas and Jim Cameron, Luc Besson made the fatal mistake of writing it himself.
(I know it feels like another incoherent litany of random complaints from Marty, but I just can't help myself. This dud is another wasted opportunity for a great space adventure and it pisses me off.)