It occurs to me that stale content and duplicates are opposite sides of a single coin.
Even if we simply assume away the issue of getting reliable duplicate identification, it only helps if new answers that cover evolving situations get enough attention to rise to the top.
The SE sites I am familiar with have a very checkered history on this.
- Some new answer to old posts rise up. But if the OP isn’t around they don’t pass the originally accepted answer in the default sort order.
- Some users actively maintain accepted answers, but that means that many of the votes are for the superseded content.
- Sometimes you see new questions like “How does foo affect bar in 2020?”. If you’re lucky the poster at lest links the old version and explains why those answer may not eb applicable any more.
The suggestions elsewhere that acceptance need not pin an answer indefinitely could help with the stale accepted answer. That or some other mechanism for community over-riding of acceptance pinning.