I disagree with this author's take on PGP. Perhaps the people they communicate with reply in plaintext, quoting the author...but that's not my experience. That type of behavior is an opsec failure, not a PGP failure.

A tool (like PGP) does not imply a privacy-guaranteed scenario. For an analogy, carrying a handgun does not make you James Bond, and carrying a lockpick does not make you a locksmith. They are just tools, and possessing one of them [like PGP] does not intrinsically include the knowledge and ability to use that tool properly.