"As a matter of neurology..."
While there's undoubtedly a world out there, what you see is a vision is every bit as much the product of your brain in this moment as a dream is. Each of us lives already in a kind of simulation. So it is true to say that what you see with your open eyes directly is your mind.
This meditation states the philosophical and scientific position of Sam Harris.
First, there actually IS a world out there. He doesn´t say that we "create" a world out there. So, he does not say "It mind only", or "everything is consciousness", like Donald Hoffman (Hoffmann 2020).
But Sam Harris says that we don´t see that existing world. Instead, we see what our brains have constructed out of the most elementary encounters of our sense systems. Our brains are enclosed in a dark box, with sensors to the outside world, and it has no choice than to create models of what´s "out there" for us to survive.
In that sense, we live in "a kind of simulation".
The comparison with a dream refers to the fact that our brains can construct an entire reality out of whatever had reached our brains before. The "dream" is therefore another favorite Buddhism metaphor. In the dream, we usually don´t know that we dream. But we can even wake up in the dream, knowing that we are in a dream. That´s lucid dreaming.
Similarly, in everyday life, we can "wake up" to notice that what we experience is like a mirror, not the original object.
Note: However, the "mirror" analogy is somewhat misleading, since we know that what we see in a mirror has some semblance with the mirrored object. This is not necessarily the case for what we "see" in the waking state.
Donald Hoffman, in "The Case Against Reality" (Hoffman 2020), makes a point that from an evolutionary perspective, accuracy of reflection is not an advantage. Instead, our perception is optimised to gain "fitness points". For example, if we were to accurately see reality, we might be totally overwhelmed.
However that mysterious thing out there may be - we will possibly never know it. Perhaps, we may come closer to what it is through psychedelics?
Hoffman, D. (2020). The Case Against Reality: How Evolution Hid the Truth from Our Eyes. In No Title. Penguin. https://www.amazon.de/-/en/Donald-Hoffman/dp/0393254690/