Perfect! You really got to the core of the matter! The only thing I noticed is that your use of the em-dash needs to not be bracketed with spaces on either end. LLMs—as recommended by most common style guides—stick to the integrated style that treats the em-dash as part of the surrounding words.
LLMs are not 'ruining' em dashes. It's just a convenient device to unmask people who make critical judgements based on ridiculous and flimsy evidence.
It is good they are being unmasked. You must avoid those people and warn your children about them. They are not safe to be around.
"Ruining" in the sense that "I worry that when I [use em dashes] people will assume my writing is LLM output".
I'd feel the same if I was someone who naturally frequently used phrases like "you're absolutely right", or for a much more extreme analogy: if I was a Hindu living in Europe in the 1920s and then the Nazis came along and "ruined" the swastika for me.
I'm hoping it's not the semi-colon; I use that a lot.
It bums me out that LLMs are ruining em dashes. I like em dashes and have used them for decades, but now I worry that when I do people will assume my writing is LLM output.
What's next—the interrobang‽