rotane’s review published on Letterboxd :
I love Firefly (the TV show) to bits; and while this movie offers a closure to the series, it's not on the same level. The focus of the film lies too heavily on action, to the point where it gets tedious, and misses much of the far more interesting character interactions and alternative ways to end a conflict that were so great in the TV show. The ultimate reveal of what both River and the Reavers are feels tacked on and way too straightforward and simple.
Nathan Fillion is still brilliant as Mal, though, as is Adam Baldwin as Jayne, but most of the other characters (with the exception of River, obviously) have been relayed to secondary characters or even bystanders. Chiwetel Ejiofor as the nameless Operative surprises as a coldhearted, but never stupid villain.