Indeed. The readership for a well-selling comic book issue might be on the order of 10,000 people, while the audience for a blockbuster movie might be on the order of 100,000,000 people. Meaning that the audience for an MCU movie is roughly the square of the audience for a Marvel comic book. There's probably a larger percentage of viewers who have at least occasionally read a comic book, but it's likely that the vast majority never have.
Really, that's the whole point of adapting a work to a new medium -- to bring in people who aren't already familiar with the work in its original medium. And the audience for comics adaptations on radio, film, TV, and movies has almost always been larger than the audience for the original comics, which is why you so often see comic books adopting characters created for other media (e.g. Jimmy Olsen, Harley Quinn, Phil Coulson, or John Diggle) in hopes of drawing in a fraction of that much larger mass-media audience.
