Self-fulfilling prophecy.

YC startups get pre-seed funding, ridiculously good deal on their seed, access to the alumni to market, free promotion on HN etc.

Which means they are going to have a 100x better chance of surviving until PMF versus someone who is bootstrapped or has limited access to capital.

So really what you're measuring isn't what makes a good startup but rather what type of startups get you into YC. And that has changed significantly pre and post Garry Tan taking over as CEO.

Now the statistics show you want to be based in SF, team of 2-3, 30 and under and building something involving LLMs. Which is kind of understandable given that we are in a gold rush period.