Author's Saving Throw: At the end of Age of Ultron, we see Miles looking at Galactus as he appears over Ultimate New York. However, when Galactus shows up in Hunger, he had just arrived. Cataclysm #1 reveals that what Miles saw was just an image of Galactus, but it did serve as a worrisome warning for the wall-crawler.
Harsher in Hindsight: Secret Wars (2015) shows that the heroes of the Ultimate Universe only delayed the inevitable. Moreover, despite what he decided here, later stories showed Ultimate!Reed is still a villain.
It's the Same, Now It Sucks: This review from Pop Matters says that the story does not feature anything new in comparison to either previous stories of the Ultimate Marvel line or previous stories about Galactus. Stories of terrible cataclysms that cause several deaths have been done many times before in the Ultimate universe (Ultimates 3, Ultimatum, Death of Spider-Man, etc.); and so where stories where Galactus was about to eat the planet and then the heroes manage to stop him at the last minute.
Rooting for the Empire: Some people are also just happy to see Big G finally roar out of his Villain Decay, after years of serving as the cosmic punching bag for other big villains.
Then there is Cataclysm altogether. Even though it was implied that this was the end of the Ultimate Universe despite the creators saying the contrary, there were previews of Ultimate Spider-Man and The Ultimates picking up where Cataclysm leaves off on the Marvel homepage.
Strawman Has a Point: After this adventure, S.H.I.E.L.D. is closed. They failed to properly protect earth from Galactus, and allowed the infame Reed Richards to be at the Hellicarrier. Chang protests that they simply had no way to know that a monster from another dimension would show up without warning from out of nowhere, that despite the mass destruction the planet was ultimately saved, and that Richards' help proved to be vital for that success. Next to that, the argument that "someone has to pay for this" seems very weak.