5e is as deadly as every other Edition if the DM choses so.
The Encounter creation math is bollocks. You have to homebrew on this one for satisfying results imho. It also depends on your Encounter / day economy and your Players, number of Magic items, tactical battleground etc etc. For a start try this: create some of the humanoid oponents (e.g. orcs hobgoblins lizardmen or humans (evil) dwarves (evil) or whatever is a frequent humanoid oponent in your campaign) more close to Players. Give them Levels and Equipment. You do not hve to give them feats or such, but e.g. if the orc captain is 5th Level he gets These attributes 18 14 18 12 12 14, 5d8+20 HP, #AT 2, damage 1d10+4 AC 18 (for some two handed weapon and platemail). This guy will be a suitable miniboss for a Level 3 Group, and a suitable solo mob for a lvl 1-2 Group.
I take pride in balancing my main Encounters so that there is almost always a slight Chance one of the chars might die, but most often the Party will be on their last Resort when they won. That feels good to me and to my Players. But i do not do 6-8 Encounters / day but i do gritty healing (8h short rest, Weekend at inn = Long rest)