In the lion king example you weren't meant to see all of the detail the artists drew. In the Army men example the color on the digital version is nothing like the color of the actual toys.
They originally made those movies the way they did intentionally because what they wanted wasn't crystal clear images with unrealistic colors, they wanted atmosphere and for things to look realistic.
Film grain and dust can be excessive and distracting. It's a good thing when artifacts added due to dirt/age gets cleaned up for transfers so we can have clear images, but the result of that clean up should still show what the artists originally intended and that's where disney's digital versions really miss the mark.
That's the point in that Lion King frame, though. They drew it planning for it to get washed out by the sunlight effect, and when it's not it absolutely ruins the "vast crowd" effect they were going for because you can clearly see there's no more animals in the background and it's just 20 guys standing there.
I don't believe these were part of the filmmaker's vision at the time, but unavoidable. Nowadays they are added again to films (and video games) on purpose to create a certain (nostalgic) effect.
Colorizing a black-and-white film, for example, is not ever restoring the original intention or vision, even "subjectively." If the makers of a black-and-white film had been making a color film, they would have made different choices.
This does not mean that you should not colorize black-and-white films, you should do whatever makes you happy. I honestly can't wait until AI is recreating missing scenes or soundtracks from partially lost films, or even "re"creating entire lost films from scripts or contemporary reviews and cast lists, and expanding films to widescreen by inventing contents on the edges. But this will not be restoring a vision, this will be original work.
It's why they all have "motion smoothing" turned on all their TV's too. Yes, it's animation, but the Blu-rays look "higher resolution", and look "smoother" and less "noisy".
All the artistic benefits you and I see are lost on most watchers.