Of course it used the characters and relationships from the source material, but the point was that it reinterpreted them in a radically different style and tone. The show was designed to minimize the comic-book elements and make the concept appealing to audiences who wouldn't touch a comic book with a ten-foot pole. There were fans of Smallville who literally did not know it had any connection to Superman, because Superman was not a character they had any interest in and thus they didn't know that the names Clark Kent and Lex Luthor were connected to him.
This is why it's so wrong to argue for imaginary dividing lines between "adapted" and "original" stories, and why it's superficial to define that solely in terms of whether it uses the same title and character names. You can take the elements of an existing story and transform them into something that's extremely different, yet at the same time embodies the same essence. Whether an audience member sees it as basically the same or completely different depends on what side of it they're looking at. You, YLu, can look at a reinvention like early Smallville and recognize it as fundamentally the same despite its transformation, but I know another online commenter who adamantly refuses to acknowledge that an adaptation like Sherlock or Elementary is the same character as Sherlock Holmes at all, because he can't look past the surface changes. It's a matter of subjective tolerance, not an objective truth of how stories "should" be told. Originality is not a yes/no question. Most creative works are derivative in some ways and original in others. It's a continuum, not a zero-sum choice.
