We have the broken, deprecated, end-of-life, and unmaintained tags default muted so the topics don’t appear in topic lists unless you interact with the topic (or change the notification level manually), but they are still findable by search so they’re not completely disappeared.
I think I’ve seen a few plugins that haven’t been updated in a number of years, but only because they didn’t need to be and were still working perfectly well. But even if that’s something we wanted to highlight on the plugin topic, we would need some way of pulling the last update date from GitHub.