Just as older editions of D&D had a firmer baseline, they also had a more defined cap. I hate to use the word "cap", because its not exactly true, but the way the experience point system is set up, there is a point when character development stops having such an emphasis on leveling up, and more of an emphasis on how the character influences the game world (we'll call it a "soft cap"). There comes a point, typically between 200k-400k xp, when a character reaches "Name" level. The actual level may vary (9-12) but this is when a character stops rolling Hit Dice, and is presumed to have reached the upper limits of power, with further advancement being a lot more incremental in terms of hit points and armor class. From this point, goals become more obscure and narrative-driven - establishing and maintaining strongholds, attracting followers, carving demesnes from the wilderness, researching more obscure and powerful spells, and so on.
This could also be seen as a time to let those name-level characters essentially retire, fading into the background of campaign setting politics and such, letting players start new characters and reserve those high level PCs for only the most earthshaking missions. In a way, successful players "win" the game by getting to this point, or by tapping some later resources to poke a finger into the strange waters of attaining demi-god or "immortal" status.
Later editions would remove the "soft cap" of 10th level and push it up to 20th (or 30th in "epic" play). To facilitate that, the options of the game would have to get so far from the baseline as to become nearly comedic. Where once an armor class of "0" (or 20 in ascending terms) was a watermark only breached by the toughest dragons (or high-dex elves in magical plate mail), armor classes in the 40's (or -20's in descending terms) had to become commonplace. To challenge a party of say, 18th level characters, who are now presumed to continue regular dungeon crawling, you have to have dozens and dozens of extremely powerful (yet mundane and common) monsters to stock those dungeons, begging the question of how any lowly orcs, beggars, or 10th level paladins for that matter, can even exist in this nightmarish apocalyptic world.
In case the implications of the removal of the soft cap are not immediately obvious, this basically means that, no matter how powerful your character gets, there will always be a multitude of more powerful foes out there. Not one or two, mister 12th level ranger, but hordes of stuff designed to make much higher level characters wet their pants. In eight years of running and playing 3x, this seemed to convey to the players and DMs (in my experience at least) a growing feeling of "nothing's ever good enough". There was no built in mechanism like Name Level to attain, no gradual high-level power curve to ride gracefully into a well-deserved retirement and notorious spot in tavern tales and the epic poetry touted across the realms by any bard worth his salt.
The term "grind" is one often used to describe later edition combat - hours of PC bonuses and modifiers striving against heaps of monster hit points and star-trek-spaceship-force-field-level armor classes until one emerges the statistical victor. But its not too much of a leap to describe an entire 20 or 30 level 3x or later campaign as a grind - when does it all end? In my experience, these campaigns ended when everyone got fed up with the needless complexity of high-level play.
If I had to pick the best publisher of contemporary edition adventures out there right now, I'd pick Paizo, hands down. Their Adventure Paths are consistently well-thought out, entertaining, with high production values and interesting plots that make you not mind the odd railroad car so much. Yet, scanning message boards out there, you will find a whole lot more "just started Adventure Path X!" threads than you will "Just finished Adventure Path X!". Actually, I couldn't find any of the latter, but I'm assuming there must be some, just harder to find maybe. What do you do when the rules themselves are the biggest challenge to overcome for even the best adventures?
To be continued...