There's a pretty big hurdle to comprehension even without compression because we are thinking in human terms. Imagine all of the prerequisite human knowledge you overlook to even approach the concept of an encyclopedic article describing something. Aliens might share knowledge by hitting each other with telepathic darts for all we know, having a completely different understanding and implementation of information, and words might require years of study on their part to comprehend. Even the golden record carries a lot of assumptions. What we know about the universe is not necessarily final, even with rudimentary things like information theory.
In the end it's a bunch of bytes, numbers really, on a disc. What are numbers, even? What if they have a totally different non-numeric system to quantify and explain their existence?
Think about finding an extraterrestrial storage device like this from our perspective. I'd safely predict 20 years before we even extract one byte of data, and a lot of that time would be arguing over it, probably. Although thinking about an alien Nobel ceremony for cracking the "extraterrestrial ceramic Wikipedia" is a pretty amusing thought.