Anon finds a plot hole

What a shit name for a war tbh. "Yo guys this was fun, but this is the last time we're getting together" - elves probably. Or maybe they meant last as in "previous", but that's just asking for it to get outdated.

Middle Earth's magic is in decay by the third age. The elves are literally leaving it, and there are way less of them. Men also only live to ~80 instead of living for hundreds of years like they did in Numenor. Middle Earth eventually becomes a world like ours.

No, not really. The trope is called "medieval stasis" (in TVT terms anyway) and is fairly common in high fantasy, though. The setting is supposed to be swords and horses, with notes of "technology bad" - which makes sense because what passes for tech in Middle Earth is mostly Saruman fucking around with orcs and that sort of thing.

As for weakening, a lot of that had to do with other things than just technological stagnation.

The war was so hard on elves that the entire race was in decline, and most of them had already fled Middle Earth for Valinor by the time of the movies. At least 2 of the greatest dwarven cities were destroyed...1 by a dragon and one by a Balrog. Humanity was divided, and the greatest human city had been without a legitimate ruler for centuries. On top of all that, the most powerful wizard, who should have been a bulwark against Saurons return, was a double-agent and had likely been undermining the other races for decades or longer. Middle Earth was basically the remains of the Roman Empire during the Dark Ages

There was some advancement in technology: Saruman invented bombs.

Especially considering how long some of the races live. Imagine how specialized in a specific field of science an elf could be when it can study a subject for hundreds of years.

I never finished the Silmarillion, but from a synopsis I read, he was defeated first, then the ring was cut from his hand.

I’ve only read the first book, but I don’t actually recall them mentioning explicitly that his finger got cut off in the way the movies did it

Yes, but the rest is very different.

The last alliance spend years preparing and forging elven weapons for the human/elf army, then they marched south along the Anduin and kicked major ass in the Battle of Dagorlad. The elves almost ruined it, because the sindarin didn't want to listen to the Noldorin Gil-galad, so they charged and got their faces punched in in the Dead Marshes (well, that's what they called em after the battle anyway). A WHOLE lot more named characters died.

The Last Alliance breached the black gate, "simply" marched into Mordor, and starting laying siege to Barad-dur for seven whole years. Anarion, son of Elendil and brother of Isildur, gets crushed under a rock at some point. Sauron eventually comes out and fights Gil-Galad. Elendil, Cirdan and Elrond join in and they fight Sauron at full power. Sauron turns in Gil-galad into a pointy-eared torch and smashes Elendil to bits. But Sauron is fought down too, and only THEN does Isildur cut off the ring, banishing his spirit once again. Isildur basically kills him while he's down, not in the middle of the fight and definitely not in the middle of the battle of Dagorlad. There is also no dramatic scene at Mount Doom in the books, but both Elrond and Cirdan have a talk with Isildur about destroying the ring. Isildur takes it as payment for the death of his brother and father, and dies just two years later.

So the war of the last alliance killed the elven kings of Greenwood and Lothlorion (meaning Thranduil becomes king). Elendil, king of the Dunedain, dies and is succeeded by Isildur. There is no more king of Noldor, since Gil-galad didn't have kids.

A comma would go a long way between ass and together.