church bad

Fair enough. Direct action against her dad, and seeing reform in her country to hopefully stop it from producing more buttholes like him probably looks a lot better to her than simply blowing it all up.

so does everyone else

Byleth looks hot without her sezy frilly thights. Rhea did good with her genetics.

Robin was fine because even though they are pivotal to the plot, they play sidekick to Chrom most of the time. And you can customize them fully, use them in any class you like.

The other 2 are downgrades. Corrin, while still customizable, gets a special sword and dragon abilities so you likely stick with their base class, but his main crime is being an annoying shit of a main character that the whole world revolves around.

Byleth drops the annoying, but still has the world revolve around them, loses all customizability other than name and birthday - and honestly they should have not even bothered with that much so the voice acted lines can say anything other than "Professor" (their last name is never used either).
But being a near mute piece of cardboard that only talks in player response prompts is horrendous, like wow. So they are the most self-insert bait, yet you can't customize them at all.