First off let's be very clear that the "age" of a question is only a problem for those questions that have been closed as either off topic or not a good fit for Stack Overflow. For other "old" questions, the appropriate solution is simply to edit the existing answers and/or post a new answer with updated information. Stack Overflow is not a forum, and as such, there's no concept of linearity to posts.
The current solution is to delete the question. As you mention:
- It's "not constructive": poll-style questions where every answer is equally valid do not fit well within our model of Q&A.
- It's been closed (and should stay that way), and thus no new answers can be added to the question.
- It's unlikely that anyone who posted those answers is going to come back to update them.
Of course, if you pull the delete trigger, you'll get a flood of users claiming that the delete-happy moderators are back to their old tricks of destroying useful content. In fact, the above-presented logic is exactly the logic used by the moderators and 10k+ users who have voted to delete other old questions, and that hasn't exactly made everyone happy. So you've really just re-raised the central question here that we've been trying to solve in the best interest of all parties for some time now.
In light of these difficulties, it appears that on the particular question you cited, everyone has simply chosen to do nothing. They don't want it to be open, as that might suggest that it's an acceptable question, but they also haven't wanted to delete it outright, perhaps seeing the merit in many of the answers that have been posted. Bringing it to public attention here on Meta will probably bring a flood of delete votes. Whether you think that solves the problem or is a good solution, I can't say.
Posting a new question to Stack Overflow on a similar subject would not be a good choice, either, since project management is clearly off-topic. It is not something done exclusively by programmers, and there are other sites in the network that are much more conducive to such questions. If you did want to write a constructive, non-poll question, you should post it on one of those sites.