On the need for definitions, my thoughts are as follows:

1 Jim's definitions usually seem to be framed so as to include the works of Ewan Maccoll etc, a revivalist who was 'in the business' - and probably suffer in terms of this.

2 Jim's points about definitions are based on what seems to be a naïve view of the nature of definitions, especially when it comes to defining a complex cultural phenomenon such as 'folk music' - whatever that is.

Have a ponder of this introduction to the problem:
https://plato.stanford.edu/entries/definitions/

Other than that, have a nice day, and enjoy the suggested listening in the opening link.