I never played the DL modules. I never read through them all, either. But I'll say this, the world and campaign laid out in DL1 and the other early modules, it holds a lot of appeal for me. It's just D&D enough to be D&D, and just different enough from most other campaign settings (of the time) to have a lot of unique appeal. A lot of stuff is tweaked from a standard D&D setting. Stuff I like, in no particular order (spoilers ahead):
Great art (Krynn art went way downhill after the DL modules). In fact, the DL modules are beautiful in many ways. Like many of the maps.
Steel vs. gold: who cares if it doesn't make sense? It's just cool. Let the nerdy kid flow through you.
Dragons as something like angels & devils. That's just flat-out cool. Works them into the religion & the pantheon, really elevates them, in terms of fluff. Making dragons the centerpiece of a D&D campaign, what could be more D&D-ey than that? Oh, and dragonriders, natch.
It's set on a post-apocalyptic mythic (rough) equivalent of Australia. How cool is that? South is cold, north is hot. The continent(s) looks nothing whatsoever like Europe, West Asia, or North Africa. Its smaller size relative to other campaign settings give it an immediate feel without detracting from the Epic feeling of the campaign's scope. And it's post-apocalyptic, but medieval fantasy, another headsmack "why didn't I think of that?" type moment for a nerdy teenager.
Draconians. Talk about a great MM race (including their origin). Several sub-species, each with unique abilities, and a unique way of dying and trying to take the players with them. Way cooler than orcs, or most humanoid species, for that matter.
Enough new MM entries to make Krynn unique, enough old ones for it to seem familiar.
The cosmology & religion tied together. Sure, it's fairly standard high-fantasy stuff, from what I gather. But, it has two redeeming traits. 1, they detail the constellations and tie them in with the gods, Greek style. Points for that, because it just works. People love stargazing and astrology, so this works to make the fluff interesting. 2, and this is the big one, they made cleric spells something the world hasn't seen in ages. The gods withdrew from the world after the Cataclysm long before the current time (I'm not really to up on the details of Krynn; it's the broad strokes that suck me in). This lets the players be the ones to bring religion - the kind that works anyway - back into the world. This is where the creators Mormon roots really show. And it's awesome, IMO. The religion itself isn't any kind of recognizeable stand-in for Christianity, Mormonism, what have you, so it doesn't look like allegory, so much as a really, really great idea for a campaign. "Yeah, we brought divine magic back to the world." Sheesh, beat that, campaign x. It's like all the good parts of religion, without the real-world baggage. And again, it's one of those simple twists that really makes the world unique and alive.
Some really cool dungeons, at least thematically.
A good plot, at least in the beginning. But I do think some kind of prequel (the Companions' adventures before DL1) might help to build up to the reveal in DL1. The bit about the bad guys moving in the world and the good guys being held up by (spoiler) just works.
Oh yeah, almost forgot, the 3 orders of wizards, 3 moons, 3 colors of robes, etc., love it. More cheesy teen nerd stuff that just works if you don't overthink it.
Those are the ones off the top of my head.
It has its bad and meh sides, like Tinker Gnomes, Gully Dwarves (which I think aren't so bad if you use them right), and Kender.
I'd probably rewrite a lot of the flavor text. And skip the singing.
As for railroading, some of it can be avoided. E.g., the part where they're thrown into cages on carriages. A good DM can stack the odds enough so that at least 1 or 2 players (or important NPCs) wind up captured, without being heavy-handed, thus making it very likely that the players follow the wagon train even if they aren't captured themselves. Nobody's preventing a good DM from tweaking the modules a bit so they aren't as railroady.
And some other railroady parts that people complain about, I don't see as a problem. Like the Dragonarmies effectively "herding" the players. There's a giant army slowly encircling the territory the players are in, oh boo hoo, too much adventure for you? Sometime life sucks, deal.
But yes, there's definitely an element of "play out the novels!" to DL. Yes, it's cheesy high fantasy in many ways (and yes, D&D is inherently cheesy to most people). But for me this is a plus - I feel as though if I was trying to give a Blue Rose sort of vibe to just one D&D setting, I couldn't do better than Krynn.
Really, that original Krynn feels like someone's really, really good campaign/homebrew to me. It doesn't hurt that the art's beautiful and I'm an artist, so I'm a total sucker for great art.
Okay, so maybe it's all nostalgia talking, but there's no reason a good DM who knows in advance what to fix and what to watch out for can't create a killer campaign for some nerdy teenagers, and give the same nostalgia to another generation.