EntityOnView
This plugin tries to optimize user experience with naturally spawned entities by restricting where an entity can spawn. Only entities that (can be seen)/seen by a player will be spawned.

Scructure entities are not included because it is not considered natural but chunk generated entities.

Depends & Credits

For more optimization; PreCreatureSpawnEvent(Needs Paper to work) is used, also abort-spawn is only used if server brand is Paper or more.

Realistic method of this repo is taken from Sentinel