Discoverability is a huge problem on Steam because there's so many games releasing, you can't really keep up.
18,000 games is almost 50 per day on average. That's 50 titles fighting for your attention and wallet every single day.
If you don't get noticed because you didn't spend half of your development budget on marketing, or your game didn't pick up well with influencers or more traditional media like reviews, you're just kinda fucked. No matter how good your game might be.
Speaking about quality, how many of those 18k titles were uninspiring, asset flipping slop?