sarah is irrelevant to the plot but

Why is everyone hating on Sarah fuck off she's unlike those isekai female character hoes that stick to the mc the whole time. I didn't really like how the mc treated sarah i mean what's the point of keeping her lol it's not like she's also super op. The author fucked up big time when he/she introduced sarah first then later on keeps her as a zombie that gets stuck in the underworld and weird spaces the whole time. The author missed the chance to giver her a good character development honestly