The idea that Man corrupts religion for his own ends is the main theme. It is obvious that many viewers have lost the ability to actually watch a film and grasp its concepts. They complain about "no plot" when it's right there on the screen. If the film is not edited with the frenetic pace of a television commercial--it is considered slow.
Yes, there are thematic similarities to the original Wicker Man (not the pathetic Americanized atrocity made recently) but that is just due to the use of an isolated setting and Pagan religion and mythology. The plots are distinctly different.
Someone made a comment about the use of a "Zippo" lighter being somehow how bad the film was. Quick research (which obviously the filmmaker did) shows that "automatic" lighters where available by 1889 and the particular lighter shown was available in 1905! Zippo did not invent lighters--they just refined them and mass produced them for WW2. Don't claim knowledge if you don't posses it.
Another complaint was the island's village was too primitive for 1905? Really, Hand-hewn buildings look just like this. Again, every idiot who can thumb type thinks they know better than the filmmaker.
This is not a review of the film but more a review of the proliferation of useless, pointless "opinion" blurbs that people believe are reviews. A review is also not just a recounting of the plot. Just typing "this movie was a waste of time" is not relevant to anyone but the typist.
If a film about man's corruption of religion and an creepy use of Celtic/Earth mythology acting as the metaphor and some gruesome violence thrown in doesn't hold your interest maybe Transformers would suit you better.