[Inderjit Sanghera]

We see several examples of 'far reaching' military technology, in M-E , and it seems that it is the 'evil' races who tend to come up with the technological advances;

It is not unlikely that they invented some of the machines that have since troubled the world, especially the ingenious devices for killing large numbers of people at once, for wheels and engines and explosions always delighted them, and also not working their own hands more than they could help; but in those days and those wild parts they had not advanced (as it is called) so far."

Over Hill and Under Hill; The Hobbit

So 'Goblins' are credited here, with creating weapons that killed many people, but you must remember that The Hobbitwas a childrensstory and therfore Tolkien would want to provide a moral message about the evil nature of such weapons by associating them with the villianous race of his tale.

But we also find in the Fall of Gondolin(BoLT 2)that Melkor, after finding about the location and defences of Gondolin built several mechanical monsters, we also hear of flying devices in the Lost Road (HoME 5) when the Numenoreans *attempted* to build flying devices, when they were tryign to find the 'straight way'

And it is said that even those who of the Numenoreans of old who had the straight vision did not all comprehend this, and they tried to devise ships that would rise above the waters of the world

The Númenóreans of Gondor were proud, peculiar, and archaic, and I think are best pictured in (say) Egyptian terms. In many ways they resembled 'Egyptians' – the love of, and power to construct, the gigantic and massive. And in their great interest in ancestry and in tombs

Letter #131; Letters of Tolkien

Here we see that culture wise, the Dunedain of Gondor was similar to the Egyptian culture.

But I think that Tolkien intended for the 'Elven' culture to be more 'pure', for example in the Dangweth Pengolodwe learn;

The Eldar grew it in guarded lands and sunlit glades; and they gathered its great golden ears, each one, by hand, and set no blade of metal to it

This is about the growing of lembas, doesn't the statement that they 'set no blade of metal to it' imply that the Elvish culture did not wishto advance so far?