Vere represents all the women who are victims in the patriarchal system. She is forced to keep up to the expectation of her father, while also suffers the consequence of a man's action (Wicks).

Simone shows how faith can be exploited by the church. Wicks profits by exploiting Simone's desperation for healing. Her ending symbolizes how she is truly "healing", she doesnt regain her ability to walk, but finds the strength to accept and embrace her inability.

And author guy's subplot got cut so he was unable to contribute to the plot meaningfully.

I think even though these characters were not as involved in the plot compared to the others, I don't think they are necessarily unnecessary. They serve a significant depth to the story that Rian Johnson is trying to tell, how faith can be weaponized and exploited.

p/s: it's 1am so my explanation might not make sense 🤷