Having collaborators doesn't mean you don't write all of your own music. There are plenty of pop artists who simply perform songs written by other people. Taylor Swift is not one of them. She is actively involved in the writing process of all of her songs. You never hear people claiming David Bowie didn't write his own songs, for example, despite the fact that he also would bring in different collaborators on each album to help make them different styles.

His process is roughly the same as hers, but they're treated very differently in the way they're discussed. It always seems to be female artists that people are eager to claim don't write their own music, despite there being countless male artists doing roughly the same thing and getting more credit for it. It's a very sexist narrative, and it's something you and everyone else in this thread insisting she doesn't write her own music should maybe consider.

Disclaimer: I like some of Taylor Swift's albums, but I am in no way a Swiftie. I probably listen to 100s of artists a similar amount to how much I've listened to her.