(Also note that outside the web/mobile space, projects that weren't updated in a year are still young, not old. "Old" is more like 5+ years.)

The two things are related. If your typical project has a dependency DAG of 1000+ projects, a bug or CVE fix somewhere will typically cause a cascade of potentially breaking updates to play out over multiple days, before everything stabilizes. This creates pressure for everyone to always stay on the bleeding edge; with a version churn like this, there's only so many old (in the calendar sense) package dists that people are willing to cache.

This used to be a common experience some years back. Like many others, I gave up on the ecosystem because of the extreme fragility of it. If it's not like that anymore, I'd love to be corrected.