The reason why you haven’t experienced the “Nemesis” system in “Middle-earth: Avengers” and “Shadow of War” in other games is because Warner Bros. applied for a patent for it.
The patent details Nemesis System Built for these two games and found by Game Maker’s Toolkit, and discussed in the latest video you can watch below (thanks to PSU).
If you are not familiar with the Nemesis system, it basically uses memory technology, which means the game can remember actions that have become narrative content. Conversely, the more enemies in the game come into contact with them, they will remember what you did.
In the Middle-earth game, the named orc leader you kill passes its abilities to another orc. However, if you die in the hands of an enemy instead, the orc may be upgraded with a new skill and will follow you again. Orcs will also fight each other to improve the team.
And because it has been patented, we may never see exactly the same thing as it in other games. Maybe similar, but not a precise system. Currently, the closest we are to the mercenary system in Assassin’s Creed Odyssey.
As RPS points out, this is not the only system patented by game manufacturers. Bioware applied for a patent for its dialogue wheel, and Take-Two applied for a patent related to AI navigation developed by Rockstar.