I think you are making the correct choice. What you built is an app. And it seems that it is a good one. But building the business behind this app is a challenge that you do not want to pursue. So don't do it. Don't listen to those who say "get a co-founder". That wont fix anything. Your focus is not it. Sell it, move on.

I'm not even sure it is a viable business itself. Aside from advertising, it has very few options as it stands. You would need to modify the platform in order to introduce other profit channels. But you already said you don't want any more of it.