Film wasn't always perfect either. A lot of early, pre-1950s cinema has been lost because the old nitrate film stock degrades over time. And can catch fire.
https://en.wikipedia.org/wiki/Nitrocellulose#Nitrate_film_fi...
https://en.wikipedia.org/wiki/Nitrocellulose#Nitrate_film_fi...
https://www.youtube.com/watch?v=uQwQRFLFDd8
Obviously DNR and bad HDR jobs are kind of their own issue, but he focuses specifically on coloring and the notion that theatre prints are themselves often wildly inconsistent and change over time, so it can be extremely difficult to even establish a baseline for what a film was meant to look like or even what it actually looked like upon release.
As a modest 4K collector myself, it frustrates me when certain films seem to sit in indefinite limbo, but Amadeus (released this week) looks fabulous and was absolutely worth the wait, so I have hopes that the people taking their time to do right by films like Ben Hur and The Sound of Music are doing so for the right reasons.