I'll start by saying I'm ethically against LLMs, but I see this as not an LLM thing but a corporate thing.
A large part of those unfound security flaws is companies really don't prioritize revisiting old code. They don't consider refactoring for stability a worthwhile endeavor at all. So much so that I've seen managers insist the proof of concept code get shipped. LLMs have kind of helped raise awareness of that, but not really because it just gets called a security flaw. If companies didn't chase maximum profit I guarantee a large chunk of what we're seeing with people patching right and left wouldn't be a thing.
LLMs have only less to this vulnerability avalanche because people are firing the things off left and right on old code. The solution isn't to keep doing that, it's to shift culturally to not shipping until things are properly developed.