This, of course, is a matter of frame of reference. The people saying 5e is easy might have experience with 2e, which featured concepts such as saving throws against death, against disintegration, and metabolic shock. For those who don’t know or remember, all three are latin for "you die". Not a paltry 10d6+40 damage. You just die. Straight up. No appeal.
In 5e everything is negotiable. Saves, advantage, rerolls, and in the worst case you merely suffer a bit of HP damage, if it even depletes your temp HPs first, after having accounted for your damage resistance.
Anyway, the point is, you could have an imbalanced level party featuring a 6th level Barbarian and a 3rd level Fighter and they would probably both have a jolly time smashing orc skulls and adding notches to their axe handles.