Quite frankly, the idea of your existence still revolving around dungeon crawls and wilderness sprawls after a certain point stupid for many reasons.
- First of all, it's repetitive from a gameplay standpoint. The combat density of someone going from level 1 to, say, level 15 is well over a hundred of them. It's quite likely that the DM and game designers have used every trick in the book in order to distract you from the formulatic writing (THIS dungeon is made of ice, THIS kingdom is run by kobolds, etc.) and if nothing else the gameplay could use a shaking up.
- Second of all, it turns the concept of advancement into a joke. Series like Dragonball Z and Inuyasha catch a lot of shit for their power level inflation. The fact is that people can only advance in discrete units so much before the idea just becomes silly. +2 swords are cool, +4 swords are a sick joke. The game shouldn't even HAVE 8th level spells available, unless 8th level spells do something drastically different from lower-level spells. See below for an extension on this rant.
- Third of all, it breaks willing suspension of disbelief. Keeping the plots fundamentally the same while continually ramping up the power level strains credibility.
The fact of the matter is that paradigms change or at least they're supposed to change when people gain more power. A Green Arrow adventure is not the same as an Iron Man adventure which is not the same as a Dr. Strange adventure. Dense fog presents a serious obstacle to Green Arrow and a category five hurricane presents a serious obstacle to Iron Man. And a dungeon or overland travel simply should cease to be a meaningful challenge in of itself after a certain point. Look at that fucking 'what abilities do you need to eliminate in order to have dungeon crawls' thread; the question is ridiculous on its face, because high-level characters can just flat-out nuke a dungeon unless the DM is employing a 'lol no' plot device. The game needs new challenges after a certain point if you don't want to play SWAT vs. Trevor's Kindergarten class.
I've noted here that it's easier to write inconveniences that will thwart King Arthur than Superman, hence why writers are in love with keeping things King Arthur level. But if you want to write stories for Superman then you need to stop pretending that crap like a typhoid epidemic or a broken bridge is an obstacle to him. This means getting rid of the idea that adventures can continue to revolve around dungeon crawls. - Fourth of all, it creates a fundamental disconnect between the mechanics and setting. Take the deities for instance. We know they can do things like spawn races from nothing and change the seasons and recreate entire continents. And given the power escalation that D&D wanks to it makes sense that eventually Steve the Crap-Covered farmer becomes the next sun god. And if you gain vast cosmic powers it should stand to reason that you should affect the setting in significant ways. I mean several threads have been written about the social engineering and economic manipulation that a mid-level wizard can do, don't you think that at a certain point it makes sense to cut the crap and just embrace the fact that a high-level character is a deity or a reasonable facsimile thereof?
But D&D has gone out of its way to cockblock people at every turn. Very hypocritically too I might add; you can totally find Orcus and Kas and kill them, even in 4th Edition, but the game just pretends like that shit never happens and sends you on to dungeon #78. There's absolutely no reason for it, especially since the backstory of several deities is that they kicked someone's ass and stole their portfolio. There's no reason for the game to end, neither. SimCity, Dungeon Keeper, and ActRaiser, flawed as they are, gives you a reasonable deity-level feel and could be adapted to gameplay. 'The Adventures of the New Gods' can be ripe fodder for a game but will not happen if people are still in their dungeon crawl schtupfest.