It will always be easier to find a single hole than it will be to seal every one. The hackers have all the same tools, so this is an arms race that cannot be won.
It seems clear that LLMs significantly change threat model math, but this observation alone does not explain how or why; the asymmetry that you’re describing is a property of pre-LLM software as well.
Same ratio of imbalance, just with matching multipliers distributed to each side, and everybody is probably worse off because of it: I cite post-LLM-ATS hiring/job hunting.
Defenders have context that attackers don't though.