The finger of blame has been pointed by many at Milla Jovovich and her personal relationship with director Besson. Such sniping may happily fill the celebrity pages of film magazines, but it is hardly reasoned debate as to the structural failure of a movie.
In fact she copes rather well in her role as the teenage girl, chosen by God to lead an army against the evil English (so what's new!) to liberate France. Unfortunately Jovovich doesn't possess a strong enough voice to punch through the important war cries. Her acting suffers too, not necessarily from a lack of talent, but almost certainly from the herds of supposed thespians gathered around her with their former careers stuck up their asses.
You can't expect someone to deliver barnstorming, revolution-inciting performances when fellow actors are giving such feeble portrayals. But even though some of the assembled cast should know better, they're burdened with a ham-fisted script that's clumsy in its telling of what should be an inspiring, classic tale.
Luc Besson must take the blame for co-scripting a movie that is unable to deliver any solid foundation of credibility. He wisely throws in a couple of good battles but when you neither care who wins or loses, then the spectacular quickly loses its impact. But while this film might not have worked out for Besson, he has a raft of fine movies to counterbalance it against.