...and people who enjoy exploring worlds probably have a hard time enjoying exploring and figuring out what they helped create.
I disagree. Let’s use Lanefan’s paladin (from a few posts above) as an example.
Baseline (Lanefan): If the player wants to play a paladin, and if they roll well enough, Lanefan provides the order(s) that are available. The player can propose modifications to better fit his character.
Level 1: The player comes up with the order, they describe its history, the NPCs he has dealt with, and sets out its tenets, which may differ from those in the PHB.
Level 2: As above, but the player specifies that he has come to (starting town) because there is a great evil in the area, and he has sworn to defeat it. He also adds that his order has a chapter house in the town.
Level 3: As above, but the great evil lurks in the Fane of the 5 kings, 3 km outside of town, and the reason why he was sent is that there are rumors of corruption in the (town’s chapter house).
Level 4: As above, but the player states that the paladin has a personal connection to the evil (perhaps an ancestor sealed away), and it is the chapter house’s leader, Guy Biscorne, who is corrupt.
In all cases, except arguably the last one, a player who enjoys exploring the world would have very few constraints in exploring the world. Even multiplying what is created by 5 (for each player), would leave a ton of stuff to surprise the players with.
Even the last one leaves space for the characters to be betrayed by the member of the chapter house who stood up for them against Biscorne, or for the ancestor to be puppetmastered by some greater evil, or for the Fane to have sunk to the bottom of a lake in the intervening years, requiring a different approach.