Lucas claims that a movie is binary, that it either works for the audience and they ignore the flaws, or it does not work for them and the flaws are completely annoying. I think that this principle of all or nothing has merit. For example, I did not notice many of the flaws in Edge of Tomorrow (2014) when watching the film and when they eventually did occur to me it did not really bother me.
The flaws were made less important because the film was so entertaining.
But not so for Pacific Rim, at least not for me. There were so many problems and all of them attached to a very obvious and banal plot. Not even giant robots could save this movie from its plot. Here is a short list of just some of the problems in no particular order of importance: 1. If you are dying of radiation poisoning, you don't just get a nose bleed, or rather if you do, its because you are bleeding at all your orifices. But none of that really matters because the radiation has probably killed all your blood stem cells and you will be dead in less than a week, horribly, and wont have the time to lead a group of desperate men and women in a last chance struggle to save humanity. 2. I found the cultural stereotypes of the German/Cambridge scientist to be offensive, although it was supposed to be funny, 3. The mind melt with the alien thing, aside from being improbable, is just confusing. Do the bad aliens read the stupid little scientist mind or not? 4. Umbilical cords are generally for mammals, as I understand it. Are the filmmakers saying that these hideous underwater alien monsters are descended from mammals? That doesn't seem very likely from what we know of them. 5. This may sound silly, but what is the motivation of our alien menace and the big fellows on the other side of the breach? I mean what is going on? Are they just attacking because they think its fun? Are they after our women? What? 6. These big aliens although they are impressive looking seem rather average in terms of construction. If they can be filleted with (for example) giant spinning sushi knives or a sock to the jaw then it seems logical that they would respond well to a couple of dozen standard, stand-off, air-to-air missiles, not to mention MK48 torpedoes. 7. Its all very well to throw around words like "analog" in regards to EMP, but for that to work that would mean that all the control systems of the adorable Gypsy Danger would have to be analog computers, etc, and I kind of doubt it.
It is a principle of visual effects that great visual effects will not save a bad movie. That is certainly true in this case, but there are some things to note about the film that are positive, in terms of cost reduction, costume design, production design and, of course, visual effects.