I think the big issue here is that D&D adventuring day attrition was (likely) never designed for the modern encounter, encounter, boss fight, end of day structure at all. It is a remant of the system designed for the encounter, encounter, encounter, boss, loot, encounter, encounter end of day structure.
The maga dungeon structure was typically, set some goal for your delve. Then an introduction phase where you get to see some of the types of (random) encounters you could expect to find here. Then the part where they get to where they are doing their main task - where succeeding is the twist of the adventures as we then are building up the tension when the attritioned and treasure loaded heroes are trying to get trough the same type of encounters they breesed trough in the introducton, the climax being when they see the exit, and the DM does their final random encounter roll.
There is a reason hardly any computer RPG do have attrition. They excel at the encounter, encounter, boss structure. The encounters are there not to attrite, but to allow the player to practice new powers and loot gotten after the previous loot, while also allowing them to feel powerfull and for the game to show off cool effects animations, monster art and other eye candy like computer games excel at and use as time fillers nowdays. Then the boss battle is the climax, which is the only point where the player skill is actually tested in any meaningful way providing the climax.
Atrition is critical to making the megadungeon story pattern to work, but it is useless for the boss ending pattern, for the boss endinf pattern you want the character power level to be the same at the first fight and the boss fight so that you feel the contrast in power level between the goon and the boss. For the escape fro dungeon scenario the attrition is critical to create the contrast between the challenge of entering vs exiting, despite meeting the same oposition.
At a slightly different rant, small encounters work in the old school mega dungeon setting as they were quickly resolved, and serves as part of the important story beats (introduction to what to expect at the end and the challenging part after the "twist"). I am howevermore sceptical if they fulfill their role well in more complex systems like 5ed, as the time combat takes and the lack of the computer game eye candy make it harder to justify it as a way to "practice skills and feel badass", or to throw in the volume of it required to actually serve as a suitable intro-climax pair in a dungeon delve.
My take on it is that it seem like D&D 5ed is likely best off being played without attrition at all, and with only combats having some obvious immediate important meaning in context of the shared fantasy.