This should be illegal, companies should be forced to open-source games (or at least provide the code to people who bought it) if they decide to discontinue it, so people can preserve it on their own.
experiments where YouTubers downloaded and reuploaded their own video 100 times, it very quickly degrades
That just means Youtube's software uses lossy compression, that is a Youtube problem, not a digital media problem. Are you familiar with the concept of file hashing? A short string can be derived from a file, such that if any bit of the file is altered, it will produce a different hash. This can be used in combination with other methods to ensure perfect data consistency; for example a file torrent that remains well seeded won't degrade, because the hash is checked by the software, so if anyone's copy changes at all due to physical degradation of a harddrive or whatever other reason, the error will be recognized and routed around. If you don't want to rely on other people to preserve something, there is always RAID, a 50 year old technology that also avoids data changing or being lost assuming that you maintain your hardware and replace disks as they break.
Here's the fundamental reason you're wrong about this: computers are capable of accounting for every bit, conclusively determining if even one of them has changed, and restoring from redundant backup. If someone wants to perfectly preserve a digital file and has the necessary resources and knowledge, they can easily do so. No offense but what you are saying is ignorant of a basic property of how computers work and what they are capable of.