Except that the majority of people perceive realities that are highly, highly similar indicating that they are all perceiving a singular thing outside of their own experience.
There's a reason why people who deviate too far from the norm get locked up.
There's also a reason why you understand the reality that I am describing to you right now. Likely because we are both perceiving the same thing. In order for us to perceive the same thing it likely must exist as a single shared reality separate from our own internal minds.
How do you know that the realities the majority of people perceive are highly highly similar? Language alone cannot be used to deduce this since perceiving and constructing realities is rooted in the domain of qualia and the psyche.
How do you now there are people for that matter other than brain(s) in vats ?
The fact that you are willing to assume so much does not invalidate parent’s argument, merely exposes the flaws in yours.
You have heard of witnesses supposedly seeing the same event but having profoundly different interpretations haven't you? They believe them fully but what they see changes based on genetics, culture, history of the person. There are as many realities as there are people.
What happens when you gather all witnesses to watch a video recording of said event and describe the event as it happens? Do they see something different or do they see the same event? Likely they will see the same thing and the distinct descriptions that permeated the "interpretations" will disappear.
Evidence from common sense and psychology attribute the distinction in your example to flaws in human memory. No field except philosophy tries to twist it into some multi-reality concept.
There is no concrete evidence either way proving whether there is actually a shared reality or not. Additionally, it's impossible to even prove the existence of other realities outside of the reality you yourself are experiencing. I could be a figment of your imagination. Such things are impossible to prove.
But what lends evidence to the notion that there is in fact a shared reality, is the fact that we all go out and look at the sky and see that it is blue. It's that simple. Your intuition says there's a sky and that means it probably is. Don't get too lost in the philosophical mumbo jumbo because all these concepts of reality have equal probabilities of being true. But the reality or illusion that is placed in front of your eyes is the reality where multiple individuals occupy a shared reality where they all see a sky and they all say the sky is blue. That's all you got, might as well believe it.
There is an infinite bunch of realities, and the one you see is defined by your own experience only.
In other words, what you perceive is what that you are. Or that you can't perceive that what you can't accept.
Hat tip to Douglas Adams who described this idea that obvious.