[Rumil]

Another aspect (in story if you like) is that the elves appear to have gone directly to the iron age without having to do all that inconvenient mucking about with a bronze age. IIRC the Valar passed on some tips.

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. Humans have been using other weapons eg spears for far longer, simple pointy-stick ones for as much as 500,000 years allegedly and stone-tipped for at least 200,000. Whether for hunting or warfare is an open question.

So in a way the inhabitants of Middle Earth are ahead of the curve instead of behind it.

As said there's much evidence of gunpowder (whether Gandalf's fireworks and flash-bang in the goblin cave or the fires of Orthanc). Also incendiary weapons, something like Greek fire - probably naptha-based - Sauron's projectiles at the siege of Minas Tirith that kindled by some nameless art and Saruman's flame projector that burnt up an ent. Debateable how much of each is 'magic' or pyrotechnics, but to be fair most medieval observers found it tricky to distinguish between the two.

The alchemists and early gunners and 'fireworkers' were often viewed supiciously as being in league with evil forces, the whiff of sulphur probably not helping their case!