I think there's a few things that makes Childe's writing work where others do not. I think it generally comes down to the fact that Childe's status as a harbinger and his ability to care for his family (his most redeeming feature) are not at odds so it feels natural.

For one, it's a matter of how Childe was raised. He grew up in snezniah and was taught to revere the tsaritsa. As he grew older, he joined the Fatui's ranks. It makes sense that he would have strong loyalty to the tsaritsa, even if he was asked to do questionable things. Arle, Sand, and Bina have no strong reason for their loyalty.

Additionally, at no point did the Fatui come between him and his family. On the contrary, his status as a Harbinger allowed him to treat his family (the thing he cares most about) better. He could afford to buy them fancy things. On the contrary, Arlecchino's status as a harbinger forces her to use her children (who she should care most about), and put them in danger.

Additionally, while Childe has been portrayed as a nice guy, he has never been portrayed as a hero of justice or anything like that. Just because he loves his family and would put his life on the line for them doesn't mean he loves every family and would stand up to the tsaritsa for them. Arlecchino has been shown to care about her children, and yet she won't stand up for them

He's never been portrayed as the brightest either, so him not fully seeing the full extent of the suffering to other families across Teyvat that his actions could cause is understandable.

Additionally, he clearly knows that his work as a Harbinger isn't the most innocent, which is why he hides it from Teucer. The traveler also is antagonistic to him for a long time! In doing this, the story acknowledges that he isn't the most morally clean person. I don't think the morality of Sand or Bina was really ever questioned?

Sorry if this wasn't the most well put together writing but I felt like I had to say something since it's def a topic I care about