Fighting the likes of Hantengu is challenging for any Hashira, but even then, Mitsuri's battle against him was really just filler and did not truly challenge her on a meaningful level.

Source: https://www.cbr.com/demon-slayer-mitsuri-kanroji-hashira-weakest-least-interesting/

One possible reason is that Muichiro's story is more tragic and can grab a more dramatic and emotional reaction within the audience instead of a superficial reason for finding love in Mitsuri's backstory.

Source: https://www.cbr.com/demon-slayer-do-all-characters-need-tragic-backstorys/