As I grow older, my formerly stellar opinion of Clarke's work has been drifting downwards.

Really? Could you expand on why?

(I'm a fan of his work but haven't read him in years)

It just didn't seem that interesting anymore. They also lacked a grand adventure, and seemed rather pedestrian. I felt I was supposed to like Clarke, but was just bored with it.

His older works, or some of his, ah, kinda-obviously-past-his-prime works?

Scifi isn't a particularly big seller (biggest genre fiction by a huge factor is romance and thrillers). Frankly the top entries do suggest a disproportionate amount of old S.F fans.

Correct, the focus is not on science fiction.

Most users probably come over from https://www.gnod.com after discovering one of the other recommendation projects. The music one is pretty popular. Or they come via googling for "author recommendation engine" or something like that.

Clarke is at position 293:

    ...
    #292 John Flanagan
    #293 Arthur Charles Clarke
    #294 Augusten Burroughs
    ...

Similarly, Dostoyevsky at #13, Tolstoy down at #63, and Bulgakov not making the list.