If I use a package for crypto stuff, it will generally be listed as part of the project, in an include or similar, so you can see who actually wrote the code. If you get an LLM to create it, it will write some "new original code" for you, with no ability to tell you any of the names of people who's code went into that, and who did not give their consent for it to be mangled into the algorithm.
If I copy work from someone else, whether that be a paragraph of writing, a code block or art, and do not credit them, passing it off as my own creation, that's plagiarism. If the plagiarism machine can give proper attribution and context, it's not a plagiarism machine anymore, but given the incredibly lossy nature of LLMS, I don't foresee that happening. A search engine is different, as it provides attribution for the content it's giving you (ignoring the "ai summary" that is often included now). If you go to my website and copy code from me, you know where the code came from, because you got it from my website
Why is "plagiarism" "bad"?
Modern society seems to assume any work by a person is due to that person alone, and credits that person only. But we know that is not the case. Any work by an author is the culmination of a series of contributions, perhaps not to the work directly, but often to the author, giving them the proper background and environment to do the work. The author is simply one that built upon the aggregate knowledge in the world and added a small bit of their own ideas.
I think it is bad taste to pass another's work as your own, and I believe people should be economically compensated for creating art and generating ideas, but I do not believe people are entitled to claim any "ownership" of ideas. IMHO, it is grossly egoistic.