Yes we need an adjustment here - and we did tune this a little bit in the newest build, so let me know which version you have.
I do keep adjusting it because I am very worried that we are shortening our day by spending time indoors, by an hour or more. Last year f.lux was trying to stick to the "natural photoperiod" - i.e. more light around sunset - and now I've backed it off a little bit, so it "looks better".
If you can see a window around sunset, when you look outside and it is "getting dark" it is still often 500 lux outside (which would be "really really bright" indoors). The trouble is that only a tiny bit of this light gets through your windows (<1% in most cases), and so this setup means you might see an hour less "daylight" every day. I think this causes all sorts of unnecessary problems for people in the winter especially.
Not being able to see your screen is a bigger problem though, so we should make some more options here.