Rather, I want to ask the question, why was this movie weak in the ways that it was?
First: suspension of disbelief. If faced with 200 foot tall monsters that kill tens of thousands and wreck billions of dollars of equipment and property, we all know the US military will respond. First with battleships
If that doesn't work, we'll try this, especially since the target is in a known spot well away from large population concentrations.
Those are the hammers we have. The film did not suggest any reasons why these things were tried and failed. Since the target audience is quite familiar with these things, that's a problem.
I personally needed to see something about no explosions or shock waves near a Kaiju. Something that knocks out all the standard responses. This would get rid of range weapons, and turn the Kaiju/Jaeger fight into a brawl with knives, teeth, and claws, which is what we want.
The movie has a germ of a good idea: no electronics near Kaijus. This could have been seriously cool, because it means you must use a person as the control system. I think the idea of multiple people would have been even better with NO electronics and NO drift. Advanced puppets are driven by multiple people. It takes teamwork, practice, and real, visible communication, which would have worked better for communicating a storyline.
The film has another good idea: the Kaiju keep getting bigger over many years. This is fabulous, because it gives us time to develop Jaegers.
For me, the point of the film was to develop a visual language for BIG. It worked where the film used familiar references. Cars, streetlights, trucks. Water coming off the monsters worked well because water has a characteristic scale.
Once the scene moved underwater, we lost all of these familiar references. The Jaegers and Kaiju looked small underwater.
Lifting the Jaegers with helicopters, and having them inside large strong enclosures, violated the language. To be lifted by helicopters, they would have had to be fluffy. I don't want fluffy Jaegers. I want Jaegers that sink in water: denser and more heavily armored than a battleship.
And the enclosures for the Jaegers were wrong. The point of building something really big is that there isn't something bigger. Really big stuff, like a battleship, is built outside. Things like battleships don't need to be protected from the weather, and the folks that work on them don't either. Perhaps they use portable shelters. You have gantry cranes for lifting pieces into position, like this:
Finally, go take a look at that battleship pic at the top of the post again. Do you see any big air intakes? No. That's because air intakes and turbines are flimsy things that have to be carefully engineered against bird strikes. The big turbine intake on Gypsy Danger looked flimsy too. That's a problem.
I think the Jaegers should have been actuated by steam cylinders, so that as they moved great billowing clouds of steam shot out of the joints. That steam would be heated by a nuclear reactor. So we'd get explosive movement and a visual style like this: