Well, sure. If we take it to the logical extreme, it's all silly. There is no way that the average superhero (whatever that is) could have that amount of energy expenditure and/or defy the laws of physics in any kind of real world.
So we're lured in by the story, the characters, by our wish to believe in magic or its equivalent, and that combines to bring about the good ol' willing suspension of disbelief. I remember the old (well, not to me) tagline of the first Christopher Reeve movie: "You'll believe a man can fly!" Well, no. We'll agree to believe that a particular man can fly within the couple hours that we're sitting in front of the screen. We don't honestly believe that someone can propel themselves through the air with no means of thrust, who is immune to gravity and inertia.
But that belief comes with an agreement: In exchange for our forking over the ticket price and maybe buying the goodies that actually make the theater money, we will be met with a good story, compelling characters, and enough quality cinematic trickery to accept the physical impossibility of it as real for that screen time. If the story fails, if the characters leave us cold, if the effects suck or are too outlandish, then we feel cheated.
For Grandma 'n' me, if the storyline contains death and destruction past a certain level of volume or style, then it's just one we don't enjoy. Yeah, we know it's fantasy. It's all fantasy. But we've agreed to suspend that knowledge, and we can't just accept that this guy who would be so much squashed pulp in real life is valid, but the bystander who was just violated and ripped to shreds is not. The movie may have great characters, it may be presented in high-quality fashion, it may be hugely popular with people of all ages, but can still have elements that are just not to our tastes. So vive la différence! in what grabs people in the movie-going public. If a movie pulls in viewers, or drives them away, then it deserves what it gets.