Parmandur
Book-Friend, he/him
Right, exactly, the unit of time for 5E is the Adventure Day: the key is to prevent a Long Rest for an extended period of time and present challenges that use those daily resources, attritioning them over time. This is not terribly difficult, and 5E works well when pushed that way. But it also works fine if the players aren't pushed and just want to have fun.Except there isn't any real attrition of either spell slots or hit points: you get them all back every morning.
Water, food, arrows, etc. don't automatically replenish every morning; you have to track and manage their use over the longer term unless you can resupply in the field somehow.
I don't see D&D ever beong able to move away from aome form of that sort of attrition based gameplay on the systematic level and still be "Dungeons & Dragons".