It's a large number of minor points. Nothing shocking, no huge issues, and of course nothing we didn't already know. The crypto is good, if you manage it well it stands up to the NSA as far as we know... Sure, it has flaws that make it hard to use in general, and hard to use securely (no long term keys, for example, would make me less paranoid about my private key), but it's still fine despite having huge backwards compatibility.

The author is overly dramatic about it in order to make a point, to hopefully get people looking for alternatives, so that a good one might take it from pgp in the future (and continues to suggest whatsapp and signal, like, really? That's your replacement for pgp?).