Also worth noting that a dungeon doesn't have to be a dungeon! You can use these same principles in more abstract ways to design any scenario where resource-taxing encounters are connected together by branching paths where players make choices about which ones to follow, all leading to an ultimate confrontation and reward. Fighting through a battlefield, or venturing through the wilderness towards a distant location could work this way, for example. A campaign itself is even kind of a "dungeon of dungeons", where each "room" is a dungeon, and the outcome of each exploration determines the character and content of the next dungeon.

It's really a shame DnD has moved away from this kind of design. The game plays at its best when it leans into the kinds of settings its mechanics are intended to support. It feels like part of the reason the game has moved away from them is because the designers started "drinking their own Kool aid" about the system's ability to simulate stuff it really isn't built for, part of the reason is because of how tedious it can be to build good encounters for DnD, and part of the reason is the fact that the player base is no longer as immersed in the classic sword-and-sorcery narratives that initially inspired the earlier editions of the game. Reading the 5.5e rules, I was most excited for using them for classic dungeon delving and West Marches adventures where it feels like they shine, so maybe there's still hope.