People are, for some reason, under the impression that the recent downgrading of Pluto to “dwarf planet” status changes…well, anything. It’s not as if it undoes all that book learnin’ you already did in grade school. Pluto hasn’t gone anywhere. The decision by the IAU is an attempt to clarify, to offer a better and clearer definition of what a planet is. The solar system is not fundamentally different because of it.
People also seem to be forgetting (or were never aware) that Pluto itself was only discovered in 1930.
Science, and our understanding of it, changes.