A couple anecdotes about HD video:

1) I heard a Sony preservationist talk about working on a 4k version of Gentlemen Prefer Blondes. Checking a pass with a high level of grain removal, he thought, "Was Hawks always such a bad editor?"...

"This film is so much slower and less funny than I remembered!" He did another pass that kept most of the grain. The picture came back to life—it moved at a clip and the gags were funny again. The visual rhythms and textures of the grain were essential to its temporal rhythms.

2) On the Simpsons, many interior locations (esp. old ones like the house) featured walls that were just solid colors. In SD close-ups, it didn't create a problem, but when they switched to the harsh clarity of HD, the sense of space was eradicated. The characters looked flat...

like they were cut-outs pasted on the surface of the screen. All the backgrounds had to be redesigned with random spots, chips and stains so that when we lost dimensional cues like floors and ceilings, it would still look like the character standing in front of a wall, not a void

The show had long since abandoned 35mm, but the qualities of SD broadcast images still gave dimension to the drawings. In HD, this was lost.