The X from Outer Space, Invasion of Astro-Monster, and Godzilla vs. Megalon all featured out there plots involving moon men, ancient civilizations, espionage, intergalactic space travel, and other bits of silliness that only managed to get in the way of what the audience really wanted, which is monsters beating each other up.
The smartest thing Pacific Rim does is find a way to keep the people a vital part of the story without distracting us from the action. Pulling from a wide range of influences including mecha anime, kaiju, the Cthulu mythos, and Top Gun, Pacific Rim is a giddy, breathless action movie that revels in it's trash fiction roots. Self aware but not overtly so, this movie is not afraid to get dumb if it means being able to have more fun. This approach could have killed this film, but under Guillermo Del Toro's direction it gives the movie a quality that instead makes it an absolute joy to watch.
The film takes place seven years after the beginning of the Kaiju Wars, where gigantic monsters rose out of a portal to another dimension that exists at the bottom of the pacific ocean. To combat this, humanity built gigantic robots called Jaegers that, piloted by humans, fight the monsters mano el mano. But the attacks have grown more frequent in recent years and the government has recently shut down the costly Jaeger program. Commander Stacker Pentacost (Idris Elba) decides to give the Jaegers one last go at destroying the monsters forever. To do this he assembles a team of the best Jaegar pilots out there, including Raleigh Becket (Charlie Hunnam) who is haunted by the death of his brother, Mako Mori (Rinko Kikuchi) a Japanese rookie and Pentacost's protege, and Australian hot shot Chuck Hansen (Robert Kazinsky). While they prepare for their final standoff, kaiju fanboy Dr. Newton Geizler (Charlie Day) and by-the-numbers Dr. Hermann Gottlieb (Burn Gorman) try to crack the secret behind the attacks, which lead them into the circle of black market merchant and kaiju body parts smuggler Hannibal Chau (Ron Perlman).
The plot of the movie is pretty bare-bones in terms of subtext and greater meaning, which isn't necessarily a bad thing when it comes to monster movies. There is some stuff involving the connection between the two pilots of each Jaeger. You see, the neural strain involved with controlling a Jaeger is too much for just one person, so each robot requires 2 pilots, one for the left side and one for the right. The pilots minds become connected because of this, similar to Sym-Bionic Titan, so in order to properly control the Jaeger both must be able to trust each other and be able to smoothly work in conjunction with them. This leads to some pretty good moments, as when we learn of Mako's motivation for fighting the kaiju as well as Raleigh's separation from his brother mid-battle.
The theme of "working together to save everyone" also applies to the film as a whole, which is far more internationally minded then the typical summer actioner. As Tasha Robinson at the newly formed and fantastic film site The Dissolve points out, this is one of the few action movies in recent years that doesn't use 9/11 as it's starting point when it comes to visualizing it's battles. From their categorization on a 1 through 5 scale to the coastal cities being the main targets for destruction, the kaiju are much more evocative of natural disasters like hurricanes and tsunamis then any human threat. The mass evacuations and shelters, as opposed to the nuclear threat of the original kaiju movies, bring to mind images of Staten Island after Sandy, Indonesia after the 2004 tsunami, or Japan in the days after the Tōhoku earthquake. Additionally, the monsters do not feel like a surprise attack or a sudden threat, they are instead like an inevitability, with ticking clocks counting down to their next strike.
This may explain why the fight sequences in the film are not presented with the now common shaky-cam. The action is not presented as a newscaster who happens to be caught in the middle of a fight, but is instead staged and presented like a wrestling match. This gives the film a more cinematic look then a lot of recent movies lately, such as Man of Steel, and may be part of the reason why it's easier to stomach the destruction. We've gotten the lip service that the cities have been evacuated, the fights often start in the open ocean, and overall the destruction feels much less exploitative then other movies that imply thousands of people are dying during every superhero fight. Instead it's more like a closed set, and actors in rubber suits are playing with props.
The less immersive feel is probably the ultimate key to this movie's success. The lasting popularity of kaiju movies lay in their artificiality. You can see the rubber suits, the strings on the jet planes flying by show, and the lip sync doesn't even match up. It's no different here. The CGI is clearly aiming at fantastical as opposed to realistic, the kaiju themselves are designed in a way that would make Ishirō Honda proud, and at one point all power is shut down by an electromagnetic pulse, but one Jaeger is still able to run because it's "analog". But that's okay, we sometimes want to be held at arms length from our entertainment. Maybe getting under the surface of a movie just isn't necessary when the surface itself is so darn purty. On the Wicker Scale, Christopher Lee decided he's cancelling the apocalypse.