I've told this story before.
Years ago, my brother and I were excited to finally see 2001. It was decades after its release, and it was to be shown on TV. I hand-wrote my brother an official invitation to 'join a viewing of the classic cinematic masterpiece, 2001 A Space Odyssey', complete with drawings of a space station. We had bowls of munchies and drinks, and we sat down to watch.
At the end, we looked at each other and said, 'WTF did we just watch??' We didn't get it at all.
We have a different perspective on the movie now, but back then, we were so used to high action / high exposition movies like Star Wars et al that something as subtle and philosophical as 2001 was lost on us.
The 4k transfer cited above is probably a result of the work Christopher Nolan headed to restore the movie from the original negatives. This version even played locally in Australia, although I didn't get the chance to see it.
https://www.vox.com/culture/2018/5/17/17349312/christopher-nolan-2001-space-odyssey-unrestored-stanley-kubrick-cannes-review