the male characters are in nearly all the leadership positions, and the female characters are left to play support.

Wow, almost like it's a traditional SHOUNEN.

Yuzuriha: primary purpose is motivation for the male protagonist

Straight up false, she's only seen as an idol before being revived (understandably so, what the hell can a stone do except look pretty). Immediately after, she's treated as a skilled member of the party. I'll give you that the author loves drawing her from behind.

Kohaku: min-maxed strength and dexterity at the loss of intelligence, wisdom, and self-initiative

Again, false. She's not dumb, if anything she's pretty smart and on top of things - only she doesn't have any knowledge of the civilized world, being a new-worlder and all that. I went through the manga, and from chapter 9 (her introduction) to chapter 26 (got bored after that), there are a total of 5 panels where she's "sexualized", all of which self-censored by either scenery or speech bubbles.

Ruri: helpless sick girl (omg that shot of her being fed medicine)

OK, that shot was "sus", as the zoomers say, but being a helpless sick girl was an essential part of the plot, not some fanservice or male superiority complex.

Kirisame: zero self-initiative (mindlessly follows orders), and that outfit makes Kohaku look like a nun

During the first half she's just a goon, which is what I'd actually like to address here - if anything, the later parts of the story lose focus and start being more about fanservice.