The Rotten Tomatoes' critical consensus of this movie reads: "Godzilla: King of the Monsters delivers spectacular kaiju action -- and reaffirms that cutting-edge effects are still no substitute for a good story." Now hold up. You had me at "spectacular kaiju action". No one should be going to this movie expecting a richly crafted and gripping plot. That would have been great, but the main point here is heavy, hard-hitting monster action, and in that department, King of the Monsters delivers big time.
Unlike the first Godzilla in 2014, which was criticized by some for limiting the screen time of the kaiju, this film puts the pedal to the metal and doesn't stop. You get several iconic Titans: Ghidorah, Mothra and Rodan, alongside Godzilla himself. Although some of the fight scenes suffer from an overuse of shaky-cam and a few too many cut-aways, overall the kaiju battles are as epic and as thrilling as they should be. There are also numerous breathtaking scenes where the CGI shines, from wide shots of devastated cities to close-ups of the kaiju. The plot, I would argue, is serviceable, and that's all you need in a big monster movie. And the human side of the story is more compelling than what we got in the first film, even if incrementally.
Long story short: if you like big action, big monsters and grand set pieces, go see King of the Monsters. If you were expecting a rich plot and well-developed human characters, this genre is not for you.