A question about advancements of weaponry

[Elemmakil]

Originally Posted by Rumil

Bronze swords are basically a pain, lack of tensile strength etc, they were made in our history, but were no match for basic iron swords, let alone well-forged steel.

Categorically untrue. Plain or wrought iron is actually softer than a good 90/10 tin bronze. Iron came into ascendence because it is much more available and thus cheaper than bronze, which requires two much rarer relatively speaking metals (copper and tin) that are generally not found in close proximity together and, in addition to their scarcity, also require extensive and sometimes long range trade networks to bring together.

[Tuor in Gondolin]

Insiladun has a key point here:

With the Istari gone, Elves dwindling and having over time less and less contact with the kingdoms of Men, it doesn't seem much of a stretch that over time the moral equation of impersonal technology designed to kill great numbers with "Morgothian" behavior would have fallen by the wayside. With that blockage gone, and always new enemies (of other Men), the motivation would have been there.

In Tolkien's Middle-earth universe men and mannish related peoples seem more easily corrupted then elves and dwarves. With the Istari also gone and the valar increasingly only indirectly montoring things you have people (including hobbits) more susceptible---see ted Sandyman and the shirreefs (a minority) who rather liked lording it over other hobbits, and the way men like Grima and the Dunlendings (and ewasterlings and Southrons by Sauron) were susceptible to dominant personalities and technological "improvements."