The quality you can get with film never ceases to amaze me. I think the Oppenheimer movie poster was shot on film then scanned digitally, and the final image is like 11k pixels wide. There was also a 1980's music clip I saw the other day on YouTube that was labelled as remastered in 4k or something, and it looked great for a remaster. Turns out it was simply re-scanned with modern tools and since the original film was so crisp it was all that needed to be done. No AI enhancement bullshit and all that.
Rescanning with modern tools is the exact definition of a remaster - Going back to the original 'master' copy and using modern techniques to produce a newer, better version :-)
Fortunately, some remasters even in gaming are the same: Going back to the source, maybe fixing some bugs, and then using the highest quality assets that were available at the time but had to be scaled down to make the game make sense for the hardware of the time. Unfortunately those are few and far between.