Here's some of my issues with the 1954 definition (for the umpteenth time). It assumes one moment in time, the mid-late C19th, was an uncompromised window on common popular music and the recorders of it were impartial. If true, they would be the only historical sources I can think of which are beyond reproach and untainted by the scientific, social and political mores of their time.
It's extraordinary that a definition which grew from the work of such collectors has survived intact until the present day without revision. It offers a closed world to all intents and purposes - read the consequences of it in entirety - an historic one that deals in centuries in an age where proliferating means of popular expression and exchange have changed the rules in unimaginable ways. It also has romantic undertones in keeping with the period that spawned it.

It contains interesting ideas, a challenge to authorship in a period marked by personal rather than community expression but takes the point to absurdity insisting anonimity is of the essense, not a consequence.
My personal opinion is the definition is either irrelevant or in need of rewriting, it is a product of its time and certainly insufficient as a tool to browbeat doubters with.