What I find Larry is that these people have never done improvisation before.It's hard for me to imagine someone laying down a nice groove, and the guitarists don't know what to do with it. Just hit a chord for crying out loud. That's unfortunate. You'd think the bass player could latch on at the very least.
They need to copy a tune and hear the drum part that they are used to hearing.
I have seen this type of musician a lot over the years.
They are parrots so to speak. They are not jammers.
They simply don't have the ability to listen to what is being played and adapt their playing to it.
They will come in with a change early if the lead guitar is stretching out a lead. They can't hear that he isn't finished yet.
They just can't listen and feel.