>>96331356
it does not say anything about automatically making every enemy you meet the same difficulty as the players
it instead recommends making things easier/harder as you see fit to keep the game moving, and with an IC explanation rather than simply making them weaker
it does mention allowing a monster to die instantly from an attack when its obvious that the players are going to win and the rest of combat is obviously just going to be burning HP
but this is not intended to make the game easier, just remove dead air

the DMG recommends what literally all other DMGs recommended: making the dungeon suited to the party level ahead of time
ie. if your players are all level 10, then you are not going to make a kobold dungeon in the first place, you make something suited to their level
but it does not tell you to make a level 10 kobold