Why is it never translating into my target language?
it's a lot less helpful than it would be otherwise. Can I change it somehow?
No, it can't be changed. Duolingo tried having more translate into the language being learned and many people quit. As they value retention, they now focus on mostly translating into your native language.
The only option is a reverse tree or laddering. My native language is English. A reverse tree is taking the English course for Spanish speakers, French speakers, and so on. Laddering would be taking French for Spanish speakers or Spanish for French speakers.
There are some translate into the target language. I find them most useful as I don't retain the spelling just from reading - mind you, I don't retain spelling just from reading in my mother tongue either since I do some sort of shape recognition that I can't fully descibe and isn't totally relevant. What is relevant is that OP is correct, lots of learning comes from translating from mother tongue to target language. Shame that others found this unappealing.
We'll just have to make the most of what there is and then work on the reverse trees and laddering as you suggest. Hmmmm Swahili from Welsh?!! ^-^