Like the OP and others above who previously had a Nexus 6P, I came to the Nokia 8 from a Nexus 5X, which has (I believe) the same camera sensor as the 6P.
I too also found the Nokia 8 camera performance disappointingly unreliable and inferior to my old N5X which generally took pleasing images first time without fuss using the Nexus /Google supplied camera app..
I suspect some of this is due to the Nexus 5X/6P camera sensor being more capable than individual rear facing camera sensors of the Nokia 8.
Specifically, though the megapixel count is quite similar, the individual photo sites in the 5X/6P sensors at 1.55µm are nearly 40% bigger than the Nokia 8 sensors 1.12 µm size. This will help the N5X/6P more in low light. That said I would have thought the dual sensor set-up in the Nokia 8 should have compensated more than it appears to do when you look at the hardware spec. Therefore I remain hopeful Nokia can improve further the Nokia 8 camera results through continued camera app development.
I hope they don't get sidetracked with the impending new model releases and forget about us in this respect. If they want to develop brand loyalty and engender repeat purchasers, to the HMD/Nokia brand they won't just leave us hanging.
Using only the colour sensor in low light seems to help as it is the one with OIS, the B&W sensor doesn't have it and just seems to add blur when the phone picks a shutter speed below 1/30th of a second.