That would have taken thousands of years in order for that to happen. There's no way the Kindom of Ikana fell more than 10 years before the event of the game
What makes you think that?
Sure there isn't much weather damage but Ikana is situated in a dry canyon and the only source of water is either far below or in a smallish well. Judging by the fact the few homes we've seen there haven't borne up well against the ravages of time i'd say it's closer to 100 years or more likely a few hundred. The Castle itself seems amazingly well preserved but that's a well noted fact of areas where it's almost constantly dry look at egypt.
Also we do see the devastation of war all over the place, the large graveyard where soldiers still patrol and even the captain is still "alive" (used in the loosest sense of the word) the Castle actually looks to have defended the rest of the valley kingdom as it's the most severely damaged in terms of non natural causes.
Also for all we know Terminians are genetically mutated from Ikana residents, just from the fall out of the war. Judging by the fact it literally becomes a city of undeath something says they dabbled with the supernatural warping them in death.
One thing interests me why does no one look at Ikana's Well? That place seems like a trial for warriors of the kingdom.
Also i'd say Ikana and the Garo Factions are Akin to the Gerudo split in Adult links life. You have one faction dedicated to gaining intelligence and the upper hand (Garo/Nabooru) they are small in number but seem to be better equipped and the other faction is akin to an army with mighty warriors (Ikana/Gerudo)
Also i do feel i need to point out something quick. It's stated in game that the undeath thing happened thanks to stone tower, so whatever happened overall is tied up to Stone Tower, i wouldn't be surprised that since the Garo Master is found in the Temple that the Garo originally inhabited the entire Stone Tower area and went to war with Ikana their closest neighbours.
Who the hell knows long term ^^, just a few thoughts to throw out .