I always thought that the key to balanced rec lists was balanced reading. I bet if you (general you) read a wide variety of books, you'd rec the same. So I do feel like challenges and quotes are useful. It doesn't mean you can never read Neil Gaiman (or whoever) again, but if you just tried to more diverse writers than usual, you'd probably find all kinds of new people you'd love.

However, when I've tried to discuss this with others, people take it very personally. And/or demand to know what I think is wrong with the default dude writers they enjoy. I haven't really had many productive conversations in this area that weren't of the preaching to the chior variety.

(I have personally given up reading Neil Gaiman forever, and am currently slogging though Andy Weir's damned Mars book, so looking elsewhere isn't really a great hardship.)