Does it? It says how managing keys in public key cryptography is complicated. As also signing and verification, and x509 certificates rely on this then one might say they too are complicated - as is everything else that builds on asymmetric crypto. I.e why encryption specifically is complicated? (Or am I just dense and missing something? :))
The poster you replied to was clearly talking about end-to-end secure encryption being complicated. This means guarding against supply chain attacks, secure sharing of keys, verification and signatures, etc.
