Ask HN: How to retain users for a one-time use app?

Hello everyone,

I recently launched a side project I've been working on, while it gets between 500-1000 users per week who actually do use it, it struggles with retention which makes sense since there's only one feature which gives a result back and you have no more use for the app. I get anywhere between 2-7% of users come back the next day and it quickly drops on days 2+.

I'm trying to figure out how to proceed building it. I've asked users for feedback on what they would like to see, but I didn't get any strong response. So I was wondering if anyone has examples of these kinds of apps which were able to grow and retain users and what they did to achieve the growth ?

Thanks.