"...what the reviewer seems to be saying, and indeed what AL Lloyd said in his book Folksong in England, was that it wasn't the pop music of its day. It was too complicated for us plebs to really get to grips with."

Where does Bert say that, WLD? Chapter & verse, chapter & verse ...

Oh, and by the way, this particular "pleb" (son of a sheet metalworker) has never had any problems in getting "to grips with it". And I've never felt excluded by the "clever folk" either (I've met quite a few of those in my time).
On the other hand I have been alienated by some of those who think that folk music is only 'yesterday's pop music' and it's, therefore, OK to replace the old songs with contemporary pop-inspired mush!