This is a problem that SO identified a long time ago but balked at attempting to solve.
There are three simple changes to the SE model which I think would be enough to deal with obsolete content:
- Problem: newer answers receive little attention because they’re sorted near the bottom, so they don’t get voted on much, so they don’t gain a chance at attention. Solution (technical): have the default sorting order take age and vote velocity into account and not just score. See How should we compute post scores?, On the value of scores and votes
- Problem: there is one way to raise an answer to the top (accepted answer), but only the asker can do that. Solution (technical): have a way for others to push an answer up. See Alternative quick votes, something like Discord's message reactions, Handling "misvoted" content - #6 by gilles
- Problem: when version 2 comes out, questions about v2 are closed as duplicates of questions implicitly about v1 whether the answers are the same or not. Solutions (cultural): edit questions and answers to include which versions they apply to as relevant; think when closing questions as duplicate about what the question means (does it actually ask the same thing, i.e. is it satisfied by the same answers?) and not just based on similarity of wording.