So, a common criticism of sci-fi/space opera settings is that they have massive dreadnoughts and tiny freighters, but there are plenty of examples in space fiction of merchant ships being bigger than any warship, they just usually are a background element, not the focus of a story.
Art by Fractalsponge: https://fractalsponge.net/field-secured-container-vessel-fscv/ And from the thumbnail of this Eckhart's Ladder video: https://www.youtube.com/watch?v=RZ54WHXPlZ8

















