Those who believe in multiple gods such as pagans will have a different view and think there is nothing wrong with this sentence at all. As far as I'm concerned, there's actually none, but that's okay. I'm just trying to get the structure of the sentence correct so I can pass the lesson.
This question should be changed regardless of what each of us believe. The fact is, the overwhelmingly vast majority of Ukrainians believe in one God and a minority believe in no god. Either way, this is a sentence that would find very little use if any in conversation in Ukraine. Moreover, many Ukrainians would find this a terrible thing to say and by trying to teach it, Duolingo is setting up its students to commit a cultural faux pax.
This isn't about culture in Ukraine. This is a sentence, nothing more, nothing less. There is no need to report and get it corrected when there is structurally nothing wrong with it. It's the same as female voices citing things in the masculine. You never know if it's a person reading a letter or what it is. Put your feelings aside from the course and do the lesson as it is.