Likening unapproved copying to theft has always been a misleading metaphor. Unlike physical theft, which is a transfer of wealth, unlicensed copies are a duplication wealth. Copying does not make anyone poorer. It makes society as a whole richer by increasing supply of creative works with no additional investment in their development. Copying might not even involve any effort or other sacrifice from the original author. Copies can be shared among people with no relation to the author.
Ironically, companies that advocate intellectual property protection the most are the ones that get closest to activity that could be sensibly described as theft. Theft involves denial of access, which is completely absent in copying, but which is the defining trait of IP law. It would be probably a stretch to accuse original authors of "stealing", because they put restrictive licenses on their own works. I am instead talking about large copyright holders that are not the original authors, that present third party works as their own property, that do not share revenue with authors, and that use a long list of shady practices to wrestle content ownership out of the hands of original authors.
Scientific journals are perhaps one of the most damaging IP rackets. Scientists are funded by governments to do research and publish papers. Reviews of these papers are done by other publicly funded scientists. Even paper selection and formatting for publication is done by scientists. So what do journals actually do? Nearly nothing. They employ accountants and sales people whose job is to collect money from scientists for access to works of other scientists. They also employ lawyers that intimidate anyone who would want to bypass the publisher and they pay lobbyists to slow down transition to open access publishing. Other than that, they just rake in profits. Damage to society is twofold. Firstly, publishers leech public money intended for research. Secondly, they delay public release of research for months, years, or even indefinitely.
Content appropriated by social media might not be as prestigious as scientific papers, but it's still valuable. Social media did not create this content. Their users did. While there are people deliberately posting content on social media for monetary gain, the vast majority of authors, producing the vast majority of content on social media, do not have any interest in monetizing their content and they never earn anything on it. They just want to make their work publicly available. As far as these authors are concerned, their works could have been released to public domain or distributed under open content license. But that is not an option. Authors are instead directed to what could be called fully automated IP theft machines, which provide, besides the technically necessary upload, a clickthrough legal agreement that transfers effective IP ownership to the social network. The new effective IP owner then takes additional technical measures to prevent "illegal" downloads of the content.
We could of course play stupid and pretend this is some form of free market agreement between uploader and social network. But it's not. Clickthrough agreements are not negotiable. Awareness of IP law issues and wider market dynamics is low among small-time content creators. Social media use network effects to establish themselves as an unavoidable monopoly that cannot be bypassed. They misrepresent themselves as authoring tools and communication tools, obscuring their true nature as large IP holders. They make it very laborious to upload the same content to other sites. Most make it hard to download one's own content. They downplay IP ownership issues and encourage carelessness and ignorance among authors. They encourage users to invest themselves into the platform before revealing licensing rules. They encourage use of proprietary formats that make it hard to move the content elsewhere, turning IP ownership into worthless formality for the author. I am pretty sure I missed several other shady practices.
In the past, social media happily pirated commercial music and movies, but the old publishers had enough money and influence to force social media to take down all the pirated content and even to implement automated detection of unlicensed copies. Too bad nobody cared to protect public domain works with the same fervor as the wealth of the old publishers. Public domain does not have lobbyists who would back it. It does not have popular "stars" created by expensive advertising. It does not have organized unions of authors who would whine they are going to die of hunger. There's no money in public domain. It's just socially valuable. Nobody cares about public value anymore.
Policies implemented to support the old publishers actually harmed public domain. They have made it way too easy to claim ownership of other people's works. It is now so bad that videos of white noise on YouTube receive several copyright violation notices. People falsely claiming IP rights on other people's works have strong financial motives. Original authors usually do not care about money or they might not even be around anymore. This results in gradual appropriation of whatever free content still exists by greedy IP holders who acquire it by simply rudely asking for it. We are now inadvertently heading towards the capitalist ideal that everything should have its owner, including every piece of content. Except that this ownership is rarely held by the people who actually invested effort into creating the content. Public domain content is largely dead while open content exists only in fiercely defended islands like Wikipedia.
We are screwed. Vested interests own the politicians. Public does not understand or care. People who care have no voice. Open content projects are inconsequential and under constant threat from greedy IP trolls. It would be so easy to fix. Just default to public domain if the author does not care and ban appropriation of public domain via both legal and technical means. It could be even framed as supporting content creators by giving social media a choice between 50%+ revenue sharing with the author and open content licensing. Social media would of course try to rearm with new battery of shady practices, but gradually improving law would eventually prevail. Third parties could then grab the public domain content and redistribute it under better terms, breaking social media hold on the market and introducing novel services and modes of distribution.
But that's not happening. Changes in IP law actually take the opposite direction. New rights afforded to companies performing digitization of works with expired copyright allow them to appropriate these works. Databases are afforded legal protection even though individual pieces of content in these databases are not copyrightable. This enables appropriation of public domain works by wrapping them in a database. The database is usually fully automatically assembled by simply aggregating submissions from website users. No actual work needed from database "curator". Open content and open source platforms are required to take down free content without court ruling, based on mere accusation, perhaps by company that competes with the free content or software. These days, any content can be killed unless someone is dedicated to defending it, possibly at great financial cost. There aren't very many free works that can survive in this hostile environment for long.