I have no idea who Dostoevsky is.......
I agree with the original post - Even as a Christian myself, I don't want sermonized at in my fiction. If I want to read a sermon, I will pick up one of Charles Spurgeon's excellent treatises or read a non fiction book. But I do want to see Christian principles portrayed positively, especially if I'm reading Christian fiction. But it doesn't have to be direct, nor does the work have to be clearly a Christian work - I do believe Christians can have a fine career writing secular fiction using this method. Subtly weaving Christian themes into the work takes skill and can be an excellent witness to those who would refuse to even pick up blatantly Christian books.
But all Christians, even those of us who focus on living our lives to glorify God in a way that is its own witness, should be ready to give an answer when asked directly - as commanded in Scripture. Write stories that can lead to that questioning, live your life so that people notice something different - its not always necessary or appropriate to use the Gospel as a hammer. But be ready when asked and be honest.
So I would agree that if a writer hemhaws around or is evasive about what they believe, I would privately wonder about the depth of their commitment. I could understand wanting to keep their witness focused on the essentials and not wanting to get into the weeds of denominational differences, but shine your light clearly!
However, even if the author waffles, that doesn't mean I couldn't enjoy anything they wrote. If its a good clean story with good values, I can enjoy it, Christian or secular because in the end, it comes down to how I perceive the story, not necessarily how the writer intended it, and if I can see my God working in the story, I can get a blessing from that, no matter if the author intended for the story to be Christian or not.
Besides, while I would probably react initially with a side eye glance at them, at the same time, its truly between them and God to work out.