Except you don't have to browse to page four of a giant thread to find out a posted solution doesn't work, and you can update an old answer when the information becomes outdated, etc.
Stale is stale wherever you put it - page four or on top. Technology moves so fast that that responses from 2009 to HTML/JS question should be just ignored no matter how green the accepted checkmark.
Other than "can I use <new API>" style questions, the vast majority of 2009 HTML/JS answers are still entirely valid.
Again, though, you're missing the point. On StackOverflow, a stale answer can be fixed, by virtually anyone. On traditional vBulletin-style forums, the post saying "this isn't true anymore, there's a better way" might be buried hundreds of posts in.
I agree with you to an extent, and this is especially true for iOS stuff where there's a lot of API/platform churn, and sometimes the same issue or bug pops up twice with a few years between.
I often land on a question that I'm asking, and it has a lot of upvotes, but it was answered 3 years ago using deprecated APIs.
If the API has really changed that much you can ask another similar question mentioning that you're interested in the new stuff, not the old one from the previous question.
Now this, my friends, is one of the major problems of stackoverflow today!