The interface between an application that wants to communicate using TLS and perform related tasks and a library that implements TLS can and should be simple -

The interface between an application that wants to communicate using TLS and perform related tasks and a library that implements TLS can and should be simple - at least for the 90% of common use cases. The whole point of the original article is that the interface of OpenSSL is horrible and undocumented. Consider how the article's author was not originally interested in looking at the internals of OpenSSL. All they wanted was a decent and documented interface for dealing with certificates; if OpenSSL had exposed such an interface, they would never even have looked at the source code of its internals.