Well said.
And I'm in the same boat. I usually find advice on the style the most useless.
What I'm looking for from workshops is:
Is my meaning clear?
Are my characters' motivation understood?
Is it engaging?
Does it read true?
Pointing out technical mistakes is always appreciated.
But to have it re-written line by line is kind of missing the point.
I'm glad you posted this because when it comes to being part of a workshop, I'm always afraid that I'm not making useful contributions.
So to have a conversation about what does and doesn't help is great.
I think a lot of critters get caught up on their own pet peeves and don't think about what state the current draft is in. There is no point nitpicking grammar if there are big worries about content, characterization, etc. I generally refuse to line edit for free--a real quality line edit takes a LOT of attention. And there is no point line editing a book still undergoing major revisions. It is better to focus on recurring issues (like if someone uses passive voice extensively) than really specific examples. If you can help someone fix their recurring issues earlier and learn what i wrong, there will be less line edits needed later.
But unless they are getting close to final draft state, it is better to focus on the stuff you said. Also things like whether the author misplaces characters, contradicts the characterization, etc.
I sure wish I had the energy and time to get back into more of this stuff right now. I tend to have a knack for it, but if I get too many things to do, I start stressing about doing enough back.
We need more people like you in writing workshops, @cmdrago! I'm with you all the way on this.
I have no doubt that your contributions are useful, btw!