I'd argue the presence of dictionaries proves the exact opposite. People realised there was an issue of talking past one another due to inexact definitions and then came to an agreement on those definitions, wrote them down and built a process of maintaining them.

In any case, even if there isnt a _single_ definition of a given subject, in order to have a discussion around a given area, both sides need to agree on some shared understanding to even begin to debate in good faith in the first place. It's precisely this lack of definition which causes a breakdown in conversation in a myriad of different areas. A recent obvious (morbid) example would be "genocide".