The firehose only ever pointed at "everyone" back when Valve was hand-picking every game that got released on Steam. Back then we only saw a few games released every week, and because of that they got that much more attention. But that also meant that most games never got any attention on Steam, since they were never released there.

However, Valve has since removed most barriers to entry and these days Steam sees more than 350 releases every week (nearly 20k in 2025), a number that is constantly growing. Add to the fact that there are already more than 130,000 games on Steam, that every new release has to compete with, and it is no wonder that median sales are low:

The low barrier to entry means that a lot of crappy games being released on Steam, that were never going to sell a lot, and the actually good games have to compete with all the other good games on the platform, that are probably also being sold at a much greater discount than your newly released title