I'm not sure if I can say this without it coming out wrong, so let me just stipulate that this is not intended as a criticism of 4e, or any other edition for that matter. Nor is it an attempt to say that 4e is "not D&D".
Regarding early 4e adventures, I suspect that the 4e design team fell victim to emergent play drift. I recall listening to the Penny Arcade podcasts before playing 4e, and it sounded for all the world to me like a classic dungeoncrawl. It really encouraged me to get back into gaming because it reminded me so much of dungeoncrawling back in the day. The Penny Arcade podcasts, of course, were done using Keep on the Shadowfell.
I think it's generally accepted that 4e's strengths are set-piece Encounters, and related to that is a strong affinity (relative to other D&D editions, at least) for scene-framing. My suspicion, though, is that this was not an explicit goal of the designers. I suspect the designers saw themselves not as redesigning D&D from the ground up, but fixing issues people had with 3e. Thus, from their POV, they still expected the game to be played roughly as it always had. KotS reflected this expectation. Dungeoncrawling is staple of D&D, particularly low-levels. Here's a dungeon to crawl in. And if you liked that kind of thing, it more or less worked at low levels. Particularly if enjoyed mixing it up with dungeon denizens.
But as characters go up in level, this starts to get out of hand. Combat starts to grind. And yet the game is very tightly designed around Encounters, and not so much in the exploring and non-encounter interaction areas. So a great many players who would go on to be 4e's biggest fans perceived a more effective way to play the game. Ratchet up the abstractness for a more narrative, drama kind of play. A chase doesn't depend on movement rates, it's a Skill Challenge. Ditto a fight with lower-level enemies. Don't worry about time keeping and enforcing "short rests" to recover Encounter powers, just move from scene to scene. Save your combats for those Encounters where you can really give full play to the 4e combat system: multiple kinds of enemies, varying terrain, etc. Reskin powers and let them allow players to take some narrative control. To be sure, this kind of play was meant to be a feature of 4e, I think, but in the beginning I don't think it was intended as the best, most effective way to play.
Thus, folks who weren't interested or engaged with this playstyle soon ran into a rut with 4e, and this led to the calls of "not D&D", while at the same time you have 4e folks saying, "Mearls never understood 4e, and his adventures for it prove it." In a sense, both were right. Mearls and the others on the design team intended for the game to be playable in ways it always had been. And for low to mid Heroic, it could be. Once you got to upper Heroic and Paragon, though, you either left the game or adjusted to play to the elements that turned out to be its strengths. Eventually the folks at WotC clued in on this as well, which is why later 4e improved.
And I think this has been an issue that's faced pretty much every edition. OD&D was intended to be played somewhat freeform, with the DM using or ignoring the rules as he wished, and players for the most part interacting with the game via verbal description. (Case in point, in the OD&D example of play, an entire combat is dispensed with the paranthetical line, "(Here a check for surprise is made, melee conducted, and so on.)") But the emergent drift there was the demand for more rules and resolution mechanics, especially for combat, and a trend towards seeing the rules as the primary method of interacting with the game. In AD&D you see basically reference books published to provide all the rules one could ever want for dungeon, wilderness, and urban exploration. But players without a wargaming background were moving the game to a more plotted, narrative playstyle, until you see Dragonlance, and a demand for settings. In 3e you had playtesters and designers thinking of the game as a cleaned-up 2e until the Magic players started to really explore interactions between feats, skills, and the rules.
And in many cases, the drift effected the reception of adventures. B2 when it came out was a fantastic sandbox adventure that left plenty of room for DMs to plug into their own campaign worlds and expand. By 2e, B2 was a joke module, with nameless NPCs, condo-dwelling monsters and no coherent story. KotS is pretty much a note for note homage to B2, with more background and story. It even has wandering monsters and denizens that move from one encounter area to another. If you like a tension-filled dungeoncrawl, it's fine, if not particularly inspired. But if you want set-piece encounters that have narrative weight, yeah, it's going to suck.