My experience is that desired features always vastly outpaces the ability for software to keep up with it, resulting in the very triaging of issues you mention

My experience is that desired features always vastly outpaces the ability for software to keep up with it, resulting in the very triaging of issues you mention - closing them quickly. The flip side of this is that most ideas never get worked on, and a lot of them do stay relevant. Sometimes the code that feature would operate on has changed significantly, sometimes the need for it has been mooted or enhanced by other changes, sometimes the change has been made significantly harder (or easier!) by other changes. But often the idea on it's own is relatively unchanged, and closed is just another form of buried - still searchable, reopenable for the right reason.