You're comparing seed funding (Y Combinator) and series A funding - most YC companies have yet to raise a series A. The other thing is that most YC companies are young and still have time to grow.
I think you're comparing apples to oranges and trying to make a quantitative conclusion.
It's fair to point out that if a company gets to Series A, it is substantially de-risked. IIRC, ~30% of YC startups get to Series A, so this milestone is material.
If a yc co from 5 years ago still hasn’t raised a series A, it’s probably dead. (I would push this to “1 year ago,” but yc invests in long term projects now like biotech.)
I think you're comparing apples to oranges and trying to make a quantitative conclusion.