Disrespecting copyright is harmful probably not necessarily to anyone explicitly, but is probably most directly harmful to copyright itself. Specifically, it depreciates the trust that content makers would place in copyright to protect their interests on works that they publish.
I agree, although I think that we ought not to treat copyright as a monolithic entity. We could amend copyright to allow at least some of what is currently seen by most people as non-objectionable piracy, such as natural persons, engaging in non-commercial infringement, while still preserving copyright in other respects, e.g. as to commercial infringement, which is less kindly looked upon by ordinary people. By tailoring what is and isn't protected according to our shared norms about copyright, we could preserve respect for it generally, while still allowing other behavior that if prohibited, would engender disrespect.
Of course, one might argue... if copyright were completely dissolved, there'd still be people who want to self-publish or would make works that could culturally enrich the society they live in without the protections of copyright. This is certainly true, but the logistical reality is that such people are not llikely to be the status quo for works of appreciable quality.
Shakespeare had no copyrights. Homer had no copyrights. Michaelangelo had no copyrights. Copyright cares about quantity not quality. The more works there are, the more quality works there are. But you can't just incentivize only quality works. If for no other reason than because it is subjective, and no one really wants the government making those sorts of decisions. God knows there's plenty of shit now. But we can ignore it.
If they were, in an age where people can pretty much self-publish already anyways, we would certainly see a very large amount of works being released where the author has actually explicitly surrendered all copyright claims, and the work is public domain.
No; that takes effort. No one is going to do that unless they really care about that.
Better to make copyright opt-in. Then only authors who really cared about having one would make the minimal but material effort to get one. The rest wouldn't bother and we would profit from their laziness. Since it would be their own decision (or lack thereof) it's totally unobjectionable.
So when you say:
The fact that even in the realm of entirely freely available content, the fact that content makers still choose to want to protect their interests
That's wrong. Most authors don't choose a damn thing, and they automatically get copyrights anyway.
a culture-starved society who must swim through an endless sea of self-published content rich with advertisements, spam, and cat-videos to find the works of quality that are out there.
We have that anyway. And culling slush piles into published works is the opposite of what copyright seeks. If anything, publishing everything indiscriminately is more in line with ideal copyright policy. (Think of all the time wasted by works that turn out to be good but which get rejected by publisher after publisher for years and only ever become known due to the doggedness of the author; we could skip all that!) Plus, plenty of bad works get published anyway. And there's not much agreement as to what's good and what's bad.
If curation is what you want, go pay a critic. But that has nothing to do with copyright.