This is exactly what I was going to say. This essay was influential to me as a young nerd, and I think it gets to the heart of the subjective/objective divide I alluded to earlier.
No matter how well you study them, a person can never know what it’s like to be a bat. They navigate by echolocation and fly! Their life is completely alien to us as visual, bipedal animals. And yet, like you said, I think the same thing applies to other people too, just to a lesser degree. The best we can do is imagine what it’s like to be someone else. But we can never truly experience it.
And while I’m no philosopher, this is what I thought “qualia” really meant. Not just “your red might look different than my red, and if we study neurons thoroughly enough, we might be able to tell,” but the idea that our subjective experiences are completely out of reach of science. As soon as you start studying them with tools and labs and sensors and whatnot, it becomes objective, and no longer counts as a subjective experience anymore, at least for the people on the outside doing the studying. That’s why qualia is a philosophical concept, not a scientific one.
But I admit I’m no expert on the topic, just an interested layman.