The sad truth is that as the game (original Vanilla) got closer and closer to launch, it was widely speculated that some corners had to be cut-- or else it might never be finished. Or, perhaps finished so late that it might already be out of style.
So we see Azshara, such a large and beautiful zone, but with very very few quests for either faction.
And Badlands, which has some quests, but no flight point for the Alliance.
Regarding Winterspring, there are quests for both factions, but WS is largely a “max level” zone so you will see quite a few quests that send you far to other zones to complete and/or pick up. (there is a darnassus quest that sends you to WS to gather feathers, and there are some quests inside Everlook that begin quest chains back in the Plaguelands.)
Also, notice even around Darkshore. Its a well-built zone with many many quests, but notice as you get around the Blackfathom Depths dungeon, it seems they didn’t even finish the artwork and landscape around it.
The Biggest Thing: If you have ever done the quests from both Alliance and Horde Side, you will see that the Alliance quests have a general theme that follows from zone to zone, and it creates a much more complete “adventure” than the Horde counterparts.
SPOILER: You see from the Alliance side that Onyxia has managed to sneak/disguise her way into the human high society/nobility, under the direction of Nefarian. From there she manages to sow seeds of discontent and disorder among the nobles, which leads to things like the Stonemasons not being paid for their beautiful work in Stormwind, which of course they become bandits and start hiding out in the Deadmines etc.
Onyxia also manages to have King Varian Wrynn kidnapped, and again while he’s presumed dead, we find very little leadership coming from the Crown at all.
[I’m a bit more fuzzy on the Horde questlines, as I haven’t done them in years, but it was certainly not as fluid containing a very centrally-themed good v evil etc. I believe these differences (in the end) come down to a gaming company that had to meet deadlines and get the game launched.]