@themanual4am It's problematic that a person can only introspect their own mind because it limits their perspective. They cannot experience first hand what it is to have another mind. They especially cannot imagine a mind of a non-human shape. This means we can't use introspection to do what those early cell biologists did: compare many diverse examples to find common themes and variations. We don't know in which ways our own minds are "typical," or what the range of mental experiences is.
Your point about observing a simpler mind is an interesting one. You're suggesting that we simplify our own minds, observing simplified activity, or a subset of activity. That is a powerful tool, but it's not the same as, for instance, observing what it's like to have the mind of a bat. Or a nematode. :)