Well, the lyrics to Shake It Off are kinda silly at times, and she is usually at her best when writing top notch lyrics, but a fun song with silly lyrics can be quite nice, especially with it's that catchy.
At that Nashville thing a few weeks back, she explained that she groups her lyrics into three sets, with Shake It Off falling into the last category:
Quill Lyrics:
"I categorize certain songs of mine in the “Quill” style if the words and phrasings are antiquated, if I was inspired to write it after reading Charlotte Brontë or after watching a movie where everyone is wearing poet shirts and corsets. If my lyrics sound like a letter written by Emily Dickinson’s great grandmother while sewing a lace curtain, that’s me writing in the Quill genre."
Example: Ivy (from Evermore)
Fountain Pen Style:
"I’d say most of my lyrics fall into this category. Fountain pen style means a modern storyline or references, with a poetic twist. Taking a common phrase and flipping its meaning. Trying to paint a vivid picture of a situation, down to the chipped paint on the doorframe and the incense dust on the vinyl shelf. Placing yourself and whoever is listening right there in the room where it all happened. The love, the loss, everything. The songs I categorize in this style sound like confessions scribbled and sealed in an envelope, but too brutally honest to ever send."
Example: All Too Well (Red)
Glitter Gel Pen:
"It lives up to its name in every way. Frivolous, carefree, bouncy, syncopated perfectly to the beat. Glitter Gel Pen lyrics don’t care if you don’t take them seriously because they don’t take themselves seriously. Glitter Gel Pen lyrics are the drunk girl at the party who tells you that you look like an angel in the bathroom. It’s what we need every once in a while in these fraught times in which we live."
Example: Shake It Off (1989)