What happened to Mordor?

[Macalaure]

There is little change in technology (unless you refer to the numerous anachronisms in the Hobbit), and warfare does not advance along technological lines (like the absence of plate armor and the use of gunpowder only after 3 full Ages of Middle-earth history).

Keep in mind that it took humanity about 4000 years from the first Pyramids in Egypt (27th century BC) to the use of gunpowder in Europe (about 13th century AD). With the first three ages lasting about 7000 years, that makes Middle-earth only about twice as stagnant as reality.