Are you asking them to give them their email ids, etc to you? If yes, then why don't you email users who haven't used the app in a long time, about news feature

Are you asking them to give them their email ids, etc to you? If yes, then why don't you email users who haven't used the app in a long time, about news features, etc and also include a feedback link there. You might get some responses. Also, try to find the uninstall rates for other todo apps. I personally in a moment of self realization decide to make todos, but the very next day I get fed up and uninstall the app, maybe thats common across a lot of users?