I feel like the indie discoverability problem is pretty bad on every platform, and cannot speak for Steam. There’s a million of them every week, and if there’s something actually good, it gets lost in that mess to all but those willing to trudge through it, or if word of mouth (Celeste) gets huge.
So, there’s some measure of props to Nintendo for using their Direct brand to do a major show for these, as well as having YouTube showcases every month. It’s how they’re using the spotlight that’s the problem — it feels like they’re intentionally targeting the stereotypical stuff that makes people hate indies.
I do agree that some kind of proper Indie section, with good curation, on the shop would solve a lot. Something as simple as an Indie Spotlight section every week, with the best of the best from years past until now, would be hugely appreciated, as well as giving favorable presence to upcoming indie games that look really good.