I think what you are missing is that in the Fifth Element, the movie was intentionally cheesy so the ending being some hamfisted and contrite deus ex machina where love saves the day is consistent with the campy themes. For a movie that was up until then a rather serious science fiction thriller that spent most of the film world building and where the audience is presented with a mystery, to then solve that mystery in a very easy and contrite way is insulting because it makes all the world building meaningless and completely flips the tone of everything. It reeks of lazy writing, which is honestly is on par with much of Nolan’s work. In my opinion great world building scifi tends to resolve the conflicts by the characters finding ways to exploit the rules of the world. That’s what separates the serious works from the popcorn.