I just saw the movie tonight and I think it's safe to say that the only way to enjoy it is to see it as a mindless action flick...
I've watched all 5 of them now and, like the other four, it's impossible to make sense of the plot because the Umbrella Corporation's motivations just don't make any sense. They've always just been evil for evil's sake. Sure, they operate with the excuse that they're "testing their weapons," but their methods of testing them become increasingly elaborate and illogical with each movie, and this one features the most elaborate and illogical of them all, which only serves as a very contrived way to show action scenes that the writers think look cool. (and bring back dead characters like Michelle Rodriguez's)
If you can see past all the ridiculous contrivances and forgive the crappy acting, (seriously, the worst acting of any RE movie) the action sequences look pretty cool. If "cool action scenes" aren't enough of a selling point for you on their own, then I'd suggest you don't see this movie.