PGP the packet formats, PGP the tool(s), OpenPGP the specs, GnuPG the tool, GnuPG the library; or any of the other libraries? Web of Trust? All of it? None of the above?

Any time this topic comes up, here and elsewhere, I find that most discussions revolve around different understandings and misunderstandings what people mean when they say “PGP”, and rarely lead to anything beyond that. - no this is PGP no you’re wrong that is PGP and so on and on…

Almost all of it, yes.

The packet format is awful, full of complexity, backwards compatibility mess, and serious security problems.

The spec is pretty awful in that a lot of the complexity is due to keeping compatibility with things that are a terrible idea. And also in that the general concept of a long lived key turned out to be a bad one.

The library or lack thereof IMO cripped PGP/GPG back when it was relevant. It's nigh impossible to make tooling for it, or it was until Sequoia showed up, which was extremely late. Things like doing stats on keys, or doing anything but what the binary wants to do were terribly painful until Sequoia.

The Web of Trust was an interesting idea for a while, but failed to transition to the modern internet.

By the time you fix all the things what remains looks nothing like PGP, so it amounts to "all of it is bad".

All of those things are liabilities (I read them carefully and mentally checked them off one by one; I'm not just being rhetorical). I wrote a sibling comment going into more detail, but happy to answer questions.

PGP: The flamethrower (kids love this one)

Each of these bad in a different and exciting way, if your idea of exciting is reading mailing list threads.

(The idea of trust networks is not bad. But PGP’s implementation of them is bad.)