I think a lot of this is due to the slide from "combat as war" to "combat as sport". Combat is given a lot of room in D&D - rule wise, time wise, effort wise. So some have started to see it as "the thing". And the encounters become "balanced" so that the PCs can show up, do their thing, and expect to win.
But in combat as war, there is no guarantee of "balanced" encounters. And the way to win is to engineer a situation where you can crush the enemy. In war, the best battle is when the foe doesn't get to fight back. You aren't there to have "manly contest of arms", you are here to win and not die.
5e definitely accommodates 'combat as war' a heck of a lot better than 4e did. A 4e D&D game where you avoided combat, or tried to ensure you only fought unbalanced easy win battles, would feel very odd. 5e goes back a long way towards allowing an older more strategic style of play I find. Although it can be run in a 4e 'my precious encounter' style, some of the spells are close to 3e 'I win buttons'; 4e definitely does 'combat as sport' the best.
IMC one 3rd-4th level PC group are in a dungeon suitable for level 1 PCs, and players having a good time. Another 3rd-5th level PC group are defending a dwarf hold from an overwhelming orc army, and players also having a good (if stressful!) time. Neither are in anything remotely balanced.