If you want 5e to go back to old school dungeon crawling, you need to have your players on board first. Ie, the game has to start with wanting to make people explore multi-level megadungeons again.
From there, you pare away abilities the players have that would make dungeoneering easier. No conjuring food or water. No rope trick, leomund's, spells that grant short rests. No purchasing potions of healing. I'm not sure messing with light sources is necessary (if we assume the bad guys use light too), but you could go the extra step of banning darkvision if you don't think your players will get tired of being ambushed by goblins for the 778th time.
More important than all of this though, is you'd have to bring navigation and mapping back as things parties needed to do, along with skill checks to avoid becoming lost.
Double down on Gary's old Tricks and Traps section from the 1e DMG. Publish more megadungeons, along with whatever explanations needed for a dungeon ecology to function. Include the why of the dungeon, since I think one of the reasons they fell out of favor was there being no real explanation for why there were these extremely large catacombs laying around (never mind how the monsters and breathe and other science facts, la la la!), who built all these traps and super sturdy locked doors, and who is maintaining all this stuff.