On the other hand, there should also be zero instances of battery-burning apps, and zero instances of unkillable apps.
IMO the blame belongs mostly to the thingies that kills apps so hard that Android blacklists them, and won't start them again until the user explicitly does it. That Android has that blacklist is understandable; that "battery savers" get innocent apps added is IMNSHO offensively shoddy.
Never tried Greenify. But the two I've seen close apps in a forcible manner that Android cannot distinguish from a buggy app that crashes repeatedly when restarted. Then Android revokes the app's right to (re)start itself.
The user retains that right. But the app cannot e.g. schedule anything to be run next time the phone is on WLAN, or next time the battery is being charged.
IMO the blame belongs mostly to the thingies that kills apps so hard that Android blacklists them, and won't start them again until the user explicitly does it. That Android has that blacklist is understandable; that "battery savers" get innocent apps added is IMNSHO offensively shoddy.