Although there are some journals that are "open access" and encourage mirroring their papers, most are not so and consider mirroring their articles to be piracy

Although there are some journals that are "open access" and encourage mirroring their papers, most are not so and consider mirroring their articles to be piracy -- so until copyright law is reformed, there can never be a (legal) repository of the scientific literature, although projects like Sci-Hub exist just as things like Pirate Bay do.