When I saw “delve”, my first thought was: like the 4e delve format? Definitely not. In the more general sense, sure. We’re not always going into dungeons, but when we do (whether underground, outside, or otherwise), I use a turn-based exploration procedure. Regardless of edition I’m running, it’s tends to be pretty similar to the one from B/X.
I like the way breaking things down into turns helps track time and provides an opportunity cost. If you’re going to spend your time digging through rubble looking for treasure, then you can’t also simultaneously be on the look out for wandering monsters and also identifying the language on the mural that the monk is cleaning up. I once had my PCs decide to set a door on fire, and while they watched it burn, monsters wandered up. This wasn’t anything I decided. It was just the output of continuing to run the exploration procedure.
There are rooms in my dungeons, and PCs navigate through them, but sometimes the action happens outside of rooms. A few sessions ago (not 5e but close enough), the PCs were exploring a barrow full of ghouls. They heard something coming, so pulled back to set up an ambush. The patrol took their bait, and followed down a side passage where they could fight the patrol away from the other ghouls. The lead ghoul triggered a trap one of the PCs had set, and the warrior and that PC were able to alpha strike what turned out to be the ghoul boss before she could do anything.
Because the PCs had explored previously, they were able to use their knowledge of the dungeon to their advantage. They knew there was a safe spot as well as one that was away from the other ghouls. That’s not to say we couldn’t have improvised something, but it wouldn’t have been the same. I also like making maps, and having a concrete dungeon lets me indulge in that.
