To be fair: "This Is How You Lose the Time War" won the Hugo, Nebula, Locus, and BSFA awards for its category in each, long before BD recommended it. A lot of readers believe it was/is an excellent story; it's not surprising it got a lot of acclaim when it broke out of the fairly insular scifi reading community. (That said - everything else you mentioned is accurate. No publisher is going to find their own Bigolas Dickolas to promote their books; that's not how it works.)
****
Fanfic communities have a lot of tiny curators, both individual and group activities, to help people find the fic they like and avoid the stuff they don't like. Part of why it works as well as it does, is the lack of commercial activity. There is no "I got this for free in exchange for an unbiased review" bullshit.
(There's bias in "I decided to review this at all." If they got their free book because they found it on a park bench, would they have read & reviewed it? If they picked up the game in a bundle of 350 games for $5, make each one effectively free, would they have played through it and reviewed it?)
I buy megabundles. Lots of them. I have literally thousands of games almost nobody has ever heard of. Some are indeed gems. (A lot are... not gems. Discussions of obscurity should mention that there's a reason most obscure things are obscure, and it's not "they have not found their true audience where they can shine.") I'd love to help the people who'd like this or that particular game find it; I'm not sure there's any way to do that beyond "hang out in a few places where games are discussed and occasionally mention one that seems relevant."