What is the reason for our limited knowledge about black holes?

How do you want us to know? In 2019 they took the first image of a black hole.
This is something through which light does not pass, sir. You will say to me: The light does not pass through the wall of my house, and I tell you: I wish it were so.
Mathematics predicted in the past that there is something huge in the universe that has a very strong gravitational force, in a way that cannot be imagined.
But the proof was at the hands of Mr. Albert Einstein. in his theory of relativity. They suggest that the black hole is the focus most likely of a star that died and its fragments compressed into a small but supermassive volume due to its high density. This focus is spinning and spinning and absorbing everything that surrounds it.. literally. Even light, which is the fastest thing in the universe, enters this focus and disappears.
We don’t know much about these mysteries because nothing can approach a black hole without being swallowed up.
What’s going on inside?