I have known Jack and his good friend for many years and agree with 'Burntstump'… up to a point.
I have the advantage of loving music but not being involved in the 'business'. This gives me distance from the petty parochial preciousness and myopic tastes, having been witness to quite a lot on my visits to 'folk' clubs etc.
I do know on the business side there's always 'the luck of the draw', who you know and kissing ass. The latter was never Jack's style.

Has he got 'great' songs? Some of them, in my opinion, yes.
Has he got a great voice? That's subjective….. a lot of people think Kylie Minogue is great... for Christ' sake.
A quote from the publishing arm of The Atlantic Music Group about Jack's material, and they are Pro's!
"Your songs remind us of our personal favourites, Guy Clark, Jimmy Webb, Jerry Jeff and Ed Bruce".

There's no such thing as the best. If you think the cream always rises to the top, take a good look at who and what has made money. If that's the measure you're going to use…. You're *"~#ed!

I do know Jack does not rate himself as a 'guitarist'. He and I listen to many who truly are. He has said on many occasions, private and public, he can accompany himself well and sometimes pretty damn good.

What makes me despair is that he has been denied making a decent living by the self appointed arbiters of taste. You'll know them on sight, they're the ones with their head stuck up their ass.