This is how moneyheads think the world works: that everything is a series of monetary incentives to be linked together to make an end result. Most humans don't actually think this way, and in specific a LOT of creative work is made without calculating exactly what the profit is going to be. This doesn't mean that artists don't want to be paid, but that artists focus on making their work first and monetizing it later.

What copyright actually protects is creative industry. By assigning individualized monopolies over copying and reproduction, the publishing industry can persistently lowball the shit out of artists (who themselves undervalue their work, see above) and then reap the profits for themselves. Since the vast majority of creative work would never see market interest, it's cheaper to pay billions of dollars to the handful of known, recognizable, and marketable mega-successes than to pay smaller amounts to a far larger pool of mid-list or unknown artists. This is why unions exist in basically every creative industry: otherwise, nobody below the talent line[0] gets paid.

To put a finer point on it: right now, the unions are doing a way better job of protecting human artists against AI art than copyright is. The argument for training AI being infringing is very weak in the general case where there's no obvious regurgitation. I mean, where does your copyrighted material even 'live' in the model, if the model can't even reproduce it? However, unions can very easily just say "you can't force us to cut corners by using this tool" in their negotiations and actually get that result. Furthermore, those rulings only bind publishers that hire artists. The artists themselves can still use AI when it makes sense in their workflow, rather than when publishers think they can cheap out on shit.

The failures of Soviet communism are complicated, but if you had to boil it down to one factor, I would not summarize it as "communal ownership bad" or "collectivism bad". Collective action has its place. Furthermore, the analogy you're making between copyright and physical property is flawed[1]. The reason why physical property ownership even exists is because of scarcity - the reason why I need permission to use your car is because you can't use your car if I'm also using it.

The irony of your communism analogy is that copyright is specifically used to erode ownership in private property in a way that makes the communism haters cry communism. There's a novel form of copyright misuse as a business model in which you put software in a thing that used to not require software, call it "smart", and then use the software to enforce your own idea of what "owning" the product means, backed up by the same laws that make it illegal to copy DVDs. There are a LOT of people who would like to go back to owning their cars and computers again, and that requires rolling back copyright, not strengthening it.

[0] Hollywood-ism for "people whose contribution to the work is not marketable"

[1] And, I suspect, a by-product of having read a bunch of Ayn Rand nonsense