This post only makes the case for em dashes from a writing and expression point of you. But it misses why people now distrust em dashes - it's not about sentence structure or expression, it's the symbol itself.
I have a question to all em dash users reading this - why wouldn't I just use a regular dash in place of the normal full-length character? I have already done this several times in this very comment, and it's a very common convention on the internet. Outside publishing and other types of very high-brow writing, the fifty different variations of dashes with minor differences in length are pretty pointless, in my opinion. There's almost no scenarios where you need to make a distinction between them, what could possibly be misinterpreted because of dash length? So why not just use the regular, standard dash everywhere?
The internet convention in the 90s used to be two dashes for the en-dash character and three dashes for em-dash character. You used a space-dash-space notation that is easy to decipher but the typical dashes variants dont have spaces around them. When I read a text message I dont expect careful typography—in a book or an article I want perfection.
More importantly though, the em-dash-in-a-sentence construct is a way of thinking and the notation is of lesser importance than the way to express oneself. I dont think the current distrust is from the symbol: the LLMs love em dashes for the same reasons many of us do, and, perhaps better than most of us, they have no trouble using the correct symbol.