Copyright law needs to change.
Back in the day, a copyright measured in decades made sense, because it took that long to promote and distribute a work and derive reasonable profit from it.
Today that process takes days, maybe months (apart from the rare work that languishes, only to be "discovered" later).
Copyright should be much shorter -- a couple years at most -- with renewal available if the creator really believes the work has yet to find its audience.
The standard for abandoned works still protected under the existing system should default against the (potential) holder of the original copyright as long as a good-faith effort was made to reach them, and damages should amount to some sort of split of the profits.
One "organized" way to do it would be to have "Internet Archive" run a SETI-at-home type of daemon on your computer to use a bit of idle time and disk to store blocks (obviously there's a rich literature of decentralized file sharing which I'm not apprentice to and so please be suspicious of my suggestions as the "best" method~~but you get the idea).
A "disorganized" way could be to have a "federation" of personal archives, comprised by tools like SingleFile^0, ArchiveBox^1, and my own DiskerNet^2 -- which all in various ways make it possible for you to save web content to your own device, and. It can be then shared with others.
I think in general, aside from any legal perturbations, one should not as a general rule rely on such a single point of failure for something (to some at least) so critical. Probably humanity (or at least netizenry) needs to embrace some form (or mish-mash of various forms) of truly dcentralized archiving.
^0: https://github.com/gildas-lormeau/SingleFile