Buddhists and scientists are both empiricists or close observers of facts. But I think their domains of inquiries differ. Scientists focus on the outer world, Buddhists on the inner one.

You're reducing "illusion" to "mistake," but that trivializes the matter. Every single concept is a simplification and therefore to some extent a misrepresentation. Does that mean every act of understanding X (such as the set of dogs) by means of Y (the concept or mental model of dogs) is illusory because that kind of cognition isn't divine or perfectly complete?

An illusion, rather, is "something that deceives by producing a false or misleading impression of reality." So the point isn't just that there's a discrepancy. An illusion has to mislead.

In Buddhism, the illusion is that things seem independent, whereas in reality they're supposed to be interdependent. And what's supposed to underlie the independence is a metaphysical substance. In our case it's the self or soul, a unified immaterial entity. Instead, there's only a series of mental states.

But we can agree there's no underlying supernatural unity, and still posit a constructed unity, an emergent, collective property. Doing so helps us get by in a practical sense. We can understand how nature works by positing such generalities. Dogs work differently than cats, for example. Is that an illusion, as in a misleading error? Or is it a useful induction that makes sense of what the reality behind the natural plurality evidently generates?