[oersted]

Wouldn't a shortening of the "nostalgia period" indicate a higher degree of innovation rather than saturation?

New ideas come faster -> the "good-old-days" come earlier.

I am not claiming that this is the primary cause, just a thought.

Note that not all innovation is positive. There has also been rapid progress on predatory monetization and optimized engagement via addictive design. This may push people to be nostalgic earlier in the same way.