Even today, creation and publication has become a lot easier and cheaper since Shakespeare's times already. But people still like his work, despite a flood of new material having come out since they were first published.
Of course, Shakespeare is exceptional in his cultural cachet.
> We should adapt new copyright policies to not only preserve these works, but to push people to keep innovating.
What do you have in mind? Archiving is already mostly allowed by current copyright policies. And I'm not sure how copyright policies can 'push people to keep innovating'? At most you can try to get out of the way.
Or, if you are being sneaky, you can lobby for arcane and arbitrary censorship rules: after all, limitations breed creativity. Eg East German political jokes were a lot better than West German ones.
See also https://en.wikipedia.org/wiki/A_Void or https://en.wikipedia.org/wiki/Oulipo