I had a real eye opening experience Thursday night in this regard.
A little back history; I am recording 4 guys that played together 8 years ago for a bit.
They got back together to write another CD. Drummer, Bass player, guitarist, and keyboards/sax/vocals.

For 10 weeks there was a fair amount of time spent trying to teach the guitarist his part. Granted they were writing new songs, but after repeatedly playing the same song it would get old sometimes.

He was sick on Thursday, so just the other 3 were there.
They wrote 4 songs and recorded almost keeper tracks as demo to remember the songs. That is compared to 1 song a night previously.

The difference? These 3 know theory, they know how to listen, and they know their instruments well enough to play what they hear .. but they can also say "Yeah, for that section let's do 1-2-1-4-2-5 and hold the 5 for 3 bars", and they know what to do.

And they listen.
Magical things happen when players listen in a live setting and understand theory and song structures.

For instance during one section of a brand new song writing attempt (jam) the keyboard player started a 'call/answer' pattern. After he did it twice, the drummer had caught on and on the third call played a pretty complex pattern on his bass drum that accented the 'call'. This in turn caused the bass player to catch on, so the fourth (final) time they all accented the call, which made that whole section build up. This was very cool to hear from guys playing something they were writing (making up) at the same time. They understand theory and listen and it makes a huge difference.

When the guitar player is there he muddies things up enough to distract the other guys and they don't get the chance to listen to each other. Plus the time spent explaining what they were doing to him when he couldn't understand theory. That's like talking to someone who doesn't understand the native language.

So Thursday I had to point out the elephant in the room.
It's funny, they were all thinking it, but afraid to say it because it might cause strife between the band. Every one of them thanked me for saying it.
Sometimes being the recording engineer comes with certain freedoms. <grin>

Make your sound your own!
.. I do not work here, but the benefits are still awesome