Welcome to the world of digital archiving. It's an enormously complicated space, and even for just my own personal projects and content, I've spent a lot of time thinking about how to ensure things are future proof and can be archived easily.
As a simple example, building my personal website atop Markdown ensures that, even if the formatting can't be preserved, the core content will be since it's simple ASCII (yes, that's ignoring issues of long-term digital storage and access and so forth, but at least it's not also a bunch of binary blobs or database formats or whatnot).
Equally alarming is that fact that so much of our digital lives aren't even in our control. A historian used to be able to rely on family archives, public libraries, etc, to understand our past. A hundred years from now they'll be looking back and hoping someone somewhere preserved the contents of an S3 bucket before Amazon decided to delete it on a whim...