Ask HN: What to Do with a Side-Project

I have a side-project in a somewhat crowded area of the iOS app store. It gets around 500-600 installs per month and has decent retention. There is a path to monetisation but it requires quite a lot of investment from me time-wise to get paid features into it. I also lack a lot of the marketing and sales skills to promote it. I have ideas about another more niche app with a clearer subscription model and am considering just re-rolling and trying a the new idea. But I keep running into sunk-cost fallacies and thinking it’s better to keep investing in the existing app that has traction. Thoughts?