Building villages, following build rules, allows for a populated village to be created.
Village buildings can spawn villagers. Build a farm to spawn a farmer. Build a library to spawn a librarian. Build an iron works to spawn a blacksmith. Build a pasture to spawn a shepherd. Build a church to spawn a priest. Build a market to spawn a trader. Build a wharf to spawn a fisherman.
Build rules would include at least, finding or building a well then connecting structures to the well by path.
A simple suggestion to get the conversation started.
Some may think this is unnecessary, finicky or can be exploited.
Consider the following, iron golem farms are made by exploiting the village door rule. The simplest version is rather finicky and exploits game rules.
The necessity of this is clear, the player spawns the type of villagers they want, unlike the random result of a villager breeder; which also exploits game rules.
If exploited, it is no different than building an iron golem type farm or current villager breeder.