Inspired by this video, this datapack makes endermen only able to move when unobserved (including when obscured by blocks). Furthermore, they can only move by teleporting until they get close enough, at which point they will pursue the player with boosted speed, capable of catching up to even a sprinting player. They can also attack even while observed if the player gets too close to them.
This datapack has a few configurable options, but there is currently no centralized config menu, so settings must manually be changed via the /function
command (e.g., /function dontblink:config/endermen_stare_back/true
)