Well the artists wouldn't be able to be artists if no one could buy their content.
I don't get why creative work should be treated like it's more important than non creative works.
An artist that works for companies sell their time and effort to create stuff the company wants. A factory worker sell their time and effort to create stuff the company wants.
Yes it's a shame some movies don't get released but it's not the end of the world.
Everyone involved still got paid and if someone is looking for anything more in their work they should start their own company.
They aren't selling the right to create (whatever that means) when working on a movie though. They aren't even selling the art.
It was never theirs to begin with.
They get paid to produce art and when they have done that their job is done. Nothing wrong with that. They sell their time and skill just like any other worker. It's not like electricians own parts of your home after they have worked on it.
If they want to keep the rights they should specify that in their contracts and probably work freelance or something.