Aren't the Rust unsafes a reflection of the Zig it was ported from? However now that you're working with Rust, you're in a position to continue improving and eliminating the unsafes.
> What should I do to understand better why my churn rate is high?
A lot of products include some questions as a part of the cancellation flow to get more feedback from customers about why they're leaving. General startup advice is always "talk to customers", so at a small scale, you could also do things like offer a $25 Amazon gift card for them to get on a call where you could chat with them about why the product doesn't meet their needs.