I’ve listened to all except the first fella, on and off again and in my unqualified assessment, I think the problem is that each artist(aside from the Proclaimers) is that they all sound familiar but not as good as the original-Graham Parker is almost Springsteen like, Josh Ritter is close to early Bob Dillon-almost, and Sexsmith is almost Roy Orbinson-ish. I don’t think they just don’t have the uniqueness for separation and a specific sound that could be directly addressed to them.
I’m probably wrong but that’s what my ears hear.