No, it didn't. Because it was the wrong sort of complexity. It didn't actually aid in telling any new stories or open up any new game play. Very little of it actually even provoked creativity. Because so much of it was tied to PrC's, it was highly inflexible and didn't offer up nearly as many choices as it could have in the same amount of space. A lot of it was redundant. You don't actually need 68 different direct damage spells each with slightly different fluff about how it is dealing it's damage. You don't actually need 7 PrC's focused around being a better archer, or sixteen different ways to boost caster level. You had a ton of different classes that all boosted different ways to damage things, but which generally didn't add any new archetypes to play or styles of gameplay.
The right sort of complexity allows you to play games that you couldn't have played without it, but which at the same time can be completely ignored if you aren't playing that game. So for example, a really good mass combat system allows you to have compelling game play around the PC's leading armies into battle, which is a story that might be difficult to support mechanically otherwise. The existence of a mass combat system adds a ton of complexity, but as long as you don't decide, "Hey, I want to run a session around mass combat.", you can avoid it completely. The same goes for good rules for handling vehicles, or good rules for running chase/evasion scenes, or good rules for running non-lethal contests, or good crafting rules, or on and on and one.
For all the hardback books that WotCpublished, they never actually added much gameplay to the game. It was more like a game I used to play years ago (back when it was deep and interesting) called 'World of Tanks', where most of the additions to game play were just new very slightly different tanks to drive (and grind, and grind, and grind) - because that didn't require many resources to create.
Pathfinder actually did a little bit better job of trying to explore that space, it's just a shame so few of the minigames it introduced to extend the game are well thought out and interesting (or even compatible, as it it tended to introduce a minigame per region or adventure path, and not a coherent hole for the whole setting).
D&D almost always spends the majority of its rules on spells. But it's really interesting how little game play the spells outside of core actually added. In fact, they tended on the whole to destroy more gameplay than they created. They either tended to either be more or less the same spell reskinned with different fluff, as in the case of the hundreds of different attack spells; or else, they tended to be simplistic win buttons that solved some problem that previously required a member of a different class. What they didn't do was generally provide any depth to magic or being a spellcaster or any world building or numinous or mythic feel.
In short, you can add complexity by making your game broad, or you can add complexity by making your game fiddly and redundant. The 3e designer went the fiddly and redundant route.
