Built-in apps are merely frontends, the actual functionality is tightly integrated into the OS in the form of daemons running in the background. I very much doubt removing the frontend app disables any of the daemons, especially considering these can be used to provide APIs that apps may rely upon.

> all the functions are part of privileged bundles shipped with the OS

Luckily a lot of these can be disabled when jailbroken: https://i.imgur.com/KhGmGrf.png

It's unfortunate that you need to exploit a (different) vulnerability in order to gain full control of your devices.

What app is that?

I tried to get into cydia and such as of late, and it's a confusing ecosystem, you need to find specific marketplace links from github to browse and then alot of stuff is very legacy and not organized.

Would love to jb but it is complicated.

It's iCleaner Pro. Here's the repo you can add in Cydia: https://ib-soft.net/

Thank you! :)