Just to give you a concrete example:
We use grape-api for some of our API endpoints. I needed to set some custom cache headers for some GET API responses and was looking into gems that do that for grape. They have a list of 6 libraries in their docs [1] that they recommend.
Their newest commits were 4, 9, 9, 10, 8 and 9 years ago, respectively. This is just one example, but I would bet half of the libraries in our transitive dependency tree haven't seen any maintenance in this decade.