This year there are 8 novels that appear on either list (http://www.thehugoawards.org/hugo-history/2021-hugo-awards/, https://nebulas.sfwa.org/sfwa-announces-the-56th-annual-nebu...). I've read three (Piranesi, The City We Became, The Midnight Bargain). Piranesi isn't speculative at all, just pretty and thought provoking and foreign in a way that's difficult to describe. The City We Became and the Midnight Bargain are both interesting. I found TMB to be at points a bit heavy handed with the metaphor, but still thoroughly enjoyable and interesting. Both it and The City We Became are very openly political, in the case of The City We Became, very openly so in a very contemporary way.
That said, it's also a good way to find authors. Polk, Jemisin, and Moreno-Garcia have other books that I've read or will soon read that are all critically acclaimed and IMO very good, thought provoking, sci fi, in the way that adventure books like Sanderson's aren't (though those are still great to read). I should note that I haven't had the chance to get to Le Guin yet (except for Omelas, which is great, and I see influence of in, for example, Jemisin's Broken Earth trilogy). She's on my list, but I want to finish up basically everything by Jemsin first. Hopefully this year!
Maybe, but it seems more like an application Sturgeon's Law (90% of everything is crap). The filter of history is fantastic for leaving a lot of the poor quality stuff behind. Contemporary writing (novels, short stories) haven't been filtered for us yet. This leads me to usually favor older writing (even just 2-3 years old) over truly new stuff unless I'm a fan of the author or have received a recommendation from friends who are more voracious fiction readers than me and who I have similar taste to.