Also just having a nice butt isnt extreme sexualization. Excessive size, jiggle physics, skimpy outfits, or an unatural/exaggerated walk could be, but a nice butt is just a nice butt.
Our other options here would be not having a female character, reducing the view of the female chatacter, or having the female character not be fit/attractive while the male character likely meets or exceeds male beauty standards. Its a lot more nuanced than girl butt makes men horny IMO.