I have seen many posts where people are turning off notifications and stop using sync go save battery. Are'nt modern phones give good battery life and allow to

I have seen many posts where people are turning off notifications and stop using sync go save battery. Are'nt modern phones give good battery life and allow to use all apps ?? I have all notifications turned on + Greenify + amplify + powernap to save battery. I get 7 hours SOT on nexus 6p