Today, it's mostly power users who still mod their devices, but that's only because it requires full root access to make it happen. The Shizuku app changes that, and will hopefully bring some new and old modders back onto the scene.
Shizuku uses a unique service that allows third-party apps access to system-level Application Programming Interfaces (APIs). It achieves this through the Android Debug Bridge (ADB) interface. ADB commands are somewhat limited by nature; however, combining them with system APIs gives you a significant amount of control. You also don't have to bother learning about the Android rooting process to start using Shizuku.
Just as with the wireless debugging feature, you must reactivate the Shizuku service each time you reboot your device (if your phone is not rooted). These two methods rely on the ADB interface, which only makes temporary changes to your device without root access. Since you don't need to reboot that often these days, it likely won't be an issue for most.
Yes, only four apps are listed right now at #^https://shizuku.rikka.app/apps/
, but it will likely grow if this becomes popular.
See How to use Shizuku for ADB rootless mods on any Android device
Modding your device without root access just got a lot better