I worked for an organization who never wanted to throw an idea away, so we had 100s of backlog items.
I worked with the people outside of the team to get them to pick the top items for a "next up" list. I started at 20 and over time reduced the "next up" list down.
We then took the "next up" list and worked with the team to refine them, understand what pain was being solved, etc.
Once we were cruising along with a small "next up" list, I started dotting the rest of the backlog each week (it was on a giant wall). The older something got, the further left I moved it. It let me show the stakeholders that ideas essentially had two common paths:
1. They were relatively new and quickly moved into development
2. They were old, got older, and never happened
It was rare for them to select a 4-month old idea and put it in next up. On the rare occasions it did happen, it's because some external driver forced it (hello big customers!)
This let me further convince them that anything with 10 dots on could be removed from view.