Simple. dont upgrade the software.
Of course Apple could implement a "Turn of battery management" switch, then all the complainers can complain their iphones shut down instead.
iOS 11 transformed my 6 Plus into a stuttering mess of molasses. I've never had any stability issues whatsoever with it.
It's a transparent attempt to motivate me into buying a new phone. Careful what you wish for, Apple, because my next phone may not be an iPhone.