Some people might argue that Elton John did not change the model of singer-songwriter because he did not write all of his own songs. However, it is important to note that he was still the primary songwriter for his albums, and he was always closely involved in the writing process. He also worked closely with Bernie Taupin, who was a talented lyricist in his own right. Together, they created some of the most memorable songs of the 1970s.
Overall, Elton John was a successful singer-songwriter who helped to define the genre in the 1970s. He was able to change his musical style without losing his core audience, and he was also able to collaborate with other songwriters to create some of the most memorable songs of the era.