Turing-completeness is a statement solely about a system's ability to perform computation, in the mathematical sense of the term (take inputs, do something for

Turing-completeness is a statement solely about a system's ability to perform computation, in the mathematical sense of the term (take inputs, do something for a while, return outputs, strictly in that order). It says nothing about other desirable properties like usability, extensibility, comprehensibility, etc.