I find Nexus 7 screenshots 100℅ faithful to reality -- not sure what may be happening on your device. I, of course, like to see a
lot more text on my screen than the default Moon setup is, which may make the theme appear darker in my screenshot.
Each of us is different. To each of us, a particular theme will carry different associations. By far the best
real books I've read in my life have been
library books with just such "dirty" pages. Most of the books I'm
really interested in are out-of-print -- they simply
can't be bought, looking nice and clean. Before the invention of e-books, I spent many fruitless, frustrating years trying to hunt down this or that impossible-to-get book. And when I finally
did get it, usually via inter-library loan, and which may have taken a few
years for a particular title, the book typically arrived with this "dirty, greasy" look. And I was
ecstatic -- it was an occasion to celebrate.
And so, you see, to me, the association I have for a "nice, clean look", is: worthless, trashy book. But if it has a "dirty", smudged-all-over look? Oh boy, that must be some
quality literature!
I now avoid printed books whenever I can. But seeing that "dirty, greasy" look in Moon+ Pro gives me a sense of
triumph every time, reminding me of that pleasurable sensation of a long time ago, "The book's finally here and
I can read it!"