Since Doze was introduced in Android 6.0, it's been a constant source of pain for developers who can't keep background processes running reliably, and users who are constantly missing important notifications because the system automatically decides to kill background services. Some ROMs are worse than others, with MIUI being the worst offender and AOSP being somewhat tolerable.
DozeOff automatically disables Doze when the system is booted on your rooted device, simple as that.
On Android 12L and newer, DozeOff will also disable Phantom Process Killing.
You can also choose keep the CPU and WiFi awake at all times, but this will drain the battery very quickly.