Anything in particular you miss? One of my side projects is something similar to Instapaper/Pocket, it doesn't see as much love as it probably should but brings in a little money.
Instapaper is definitely coasting right now, and as far as I can tell they haven't made any substantive improvements in half a decade. The reader aspect doesn't necessarily need to change in that timeframe, but the web has changed, and they should be integrating with new/different things to stay current.