I think the post tries to encourage more people to start startups and to apply to YC, however, I think the way this post is formulated, it gives the impression that if you have a good idea you can simply apply, which I don't think is true at all. I think it would be really helpful to write that people should only apply to YC if they either have a track record or traction. Criterion 1 is Track record consists of these three things
1. Built/sold something impressive before
2. Worked at Facebook or Google
3. Graduated from Stanford
Criterion 2 is traction, which is either 10.000 users for consumer or $5.000 revenue for B2B after 6 months.
In summary, if the founder does not have a track record as described above or strong traction, she/he is very unlikely to get into YC. Explaining this will prevent people without a track record from thinking that they only have to have a good idea, because if you don't have a track record you need a really good idea with a huge market and traction to get in. I don't think many founders realise that.
I might be wrong, so I would love for others to critizise or add to my comment. I would love to hear about examples for instance, of a recent startup where the founders neither had a track record, nor traction.