Especially for those of us with no coding background, who can’t just build/edit an app.
For example, I like using Gadgetbridge to replace my fitness tracker app: https://gadgetbridge.org/
It’s not nearly as full-featured as a regular fitness app, but it literally can’t connect to the internet so there’s no way anyone can get my health info.
I use the duck-duck-go browser on my phone. It has kinda private mode enabled all the time.
Some wild websites complain about my adblocker then, which does not exist :)