You forget Maiev and Jarod, and forget that most of the armies that marched on Zin'Azshari come from Suramar, the Moonguard that led that army, the sentinels and priests, they are mostly from the city and surrounding regions.
No we haven't seen an interest presented in game. Sadly the game doesn't come close to giving enough detail to say that "because we don't see it being mentioned" such an interest isn't there, we left personify and imagine many of the situations and guess many things if we're interested.
I'd say this though, you're homeless, but your original city you fought a war to defend is back and available, would you say no to it? The ngiht elves loved their civilization, they loved their empire. They didn't like the attitude of the Highborne or the abuse of their precious magic (which they loved very much - hence why they hated those who were callous haughty and reckless with it) - it stands to reason they still love their original home and I wouldn't be surprised if there is desire to return.
Why would you hate Suramar? If London was fully of crime and corruption - I would say I hate it, but what I actually hate is the people committing crime and corruption and the system that empowers it. Not the buildings and streets and beautiful gardens and homes. If it was shoddily built, always falling apart, hurting the environment, or just nothing works and altogether trash heap, then it's the actual city I hate, not the people, the physical place itself.
Which do you think the Night elves who left to fight that war feel?
It could go several ways acn't it. Tbh, I like this approach the most, why? Because I want to like the Nightborne, because I like Night elves, I want the night elves restored - so I want their beautiful cities, temples and forests all going good, and ffel proud about it(even though id din't design it or write it, I just role play one - football team fans syndrome)
However we allk now that there are several ways, and blizz often do the war thing, dividing the race producing conflict. For a change i'd like some race in the opposite faction to get on well with a race in my faction. Nightborne and Night elves could be it. Nightborne of all the horde races have committed the least grievances as a race (don't know about individuals - but so far the Nightborne as a race haven't been involved in fighting the night elves) not to mention they have so much commanlity and history and age, they are perfect for showing themselves bigger than the faction conflict and rising above it, and being like parents to the younger races - being the exception that shows faction corpoeration can happen but unique enough that it isn't a common thing - who else really shares a shared bond far greater than the conflict recent sins have committed but are in different factions and are not in the faction because they hate the opposite faction? The Nightborne are the only ones in the horde that fits, and the Night elves are the ones they can most strongly connect.
However the Nightborne should extend the hand. They need to do this, to me this would show they are actually quite decent, I despite being on the horde, they recognise they owe the night elves and hate the treatment of the kaldorei. They may be friendly with the blood elves, but they are not the blood elves, they don't have to agree or like everything the blood elves like or take every position they do. They are far older, and should be leading, putting their foot back and saying "ENOUGH" this is wrong, you can either join us, or stand aside, but we're doing this, don't get in our way, this is the right thing to do.
I'd really respect them for that, showing me they have backbone, they genuinely care about what's right, and are not afraid to call out their allies for their b/s.
So far Thalyssra has been quiet an whimpish, if they turned her around or used other Nightborne like lyl'eth Lunastre, Thaedris Feathersong, Valtrois etc, then I'd respect them.
The question instead you should be asking is WHY WOULDN'T they?? Darnassus, built 20-16 years ago, has architecture all from the pre-sundering era cities, the temple of Elune is one of the smaller temple models common, the style of the Warrior building and the gazeebos are all pre-sundering style.
The rural buildings - take the rural building in Auberdine, that's the way they built rural lodges in the pre-sundering era, the lodge in winterspring has been there from before the sundering.
If you look at the night elf lore, they didn't real build anything during the long vigil. The Shen'drlaar built nothing, the NIght elves in Suramar built nothing, the ones in the Long vigil, basically left everything in ruins, the VILLAGE of nighthaven was the seat of government of the priesthood, and we don't even know if that was built during the long vigil or was a pre-sundering one. Let's say it was, but that was about it. Building and advancing life was not what the various night elven groups in the post sundering world were busy with. The Long Vigil group were all about preventing the return of the Legion, watching out for i.e. Vigil and guarding against - this is what vigil means. The druids of that group were with dragons and Cenarions sleeping for thosuands of years in caves (elegantly decorated as you can see in Val'Sharah, but caves none-theless where they spent most of their time guiding the evolution of the world via the dream with the Green Dragonflight, when awake they were patrolling nature, restoring it, and working with the Cenarions on stonetalon mountain suppressing the use of arcane magic so it's signature wouldn't leak into the twisting nether.
The night elven people, led by the priesthood, were mostly hunters, they guarded the borders, patrolled often, they are the ones that would kill any sentient being coming to the Ashenvale border to ensure no one would discover the Well, especially if they were a legion agent or just a sentient who could develop magical abilities and then repeat the same mistake the Night elves did, so they guarded it, constantly patrolling. For that group it wasn't life as normal, it certainly wasn't building cities and towns, having trade, economy, progress, infrastructure, academia theory, development etc etc - it was MILITARY duty - they basically were a militarised faction.
THe ones living lives were the ones in Suramar and Eldre'thalas, life continiues, the former ina bubble were unable to expand or anything but they continued their lives and customs, the ones in Eldre'thalas did the same thing, but alas, the way they powered their city would come to bit them in the end, causing them to begin to decline as the net power gain from Immol'thar turned to a net power loss, and the prince, under the dark cloud of demonic corruption, maddened enough to start offing his people to keep the balance a net gain, this decline begins about 1,000 years ago, and deteriorates to the point we see in classic, where the Shen'dralar are furiously trying to contain Imolthar, thezealots are in thelibraries obsessed with knowledge and study, and the prince is just lounging there.
Well the horde kill him (I think) and the Shen'dralar have to flee the city, they spend 6 years in the forests of Feralas, gaining their sanity and weaning themselves of addiction, in their right mind, they resist overtures from Queen Azsahra and decide on discovering deathwing'splan (cos they scry on everything) that they could be of mutual benefit to the Kaldorei of Darnassus. So they approach them, and as Mordant states, 10,000 years is enough time to grieve, time to move on, we need each other.
So no buildings. naturally when they start building again, guess what it is in the style they know how … this is Night elf architecture, blizzard has a set for each race. Suramar, Zin'Azshari, Darnassus, Nar'thalas, the Temples of ELune, the CoEN, Eldre'thalas, Meredil, Tel'anor, Shal'anar, Astranaar, Lor'danel, Auberdine, Mathystra, Bashal'ran, Ameth'aran, Sargeron, - these are ALL NIGHT ELVEN all of them, this is the style they have. The template was updated in Legion (blizzard do this btw, when they do new expansion and stuff - notice the orc and draenei architecture models were updated in WoD - this isn't a new style, it simply means the architecture in TBC (for Draenei) and classic (for Night elves) is replaced by the new ones in WoD (for draenei) and legion (for Night elves)..
Ah, but after following this product for 16 years (sheesh, I could almost have a kid 16 years old, cos puberty was already a few years into when I started wow), I've known directions change a lot. Nightborne going horde is not like blood elves were in TBc, Nightborne are not a core race, they are not some new symbol of the horde's right to a race, nor some permanent horde fixture. You must realise that anything can happen. THe only thing you can guarantee is that Nightborne would still be playlable on the horde. you cannot guarantee that Suramar would remain horde, you cannot guarantee that all Nightborne would remain horde, you cannot guarantee that another night elven arcane group like the Highborne wouldn't be a major equal force in the night elves or be an allied race. What if the naga return to a pseudo elven force and ally with the Night elves, working hard with the Highborne and Illidari as the race is on a warpath or some other motivation.?
What if Nightborne do decide some of us prefer the alliance, and we don't care what the blood elves thinking, we determine our destiny, is that beyond blizzard to write? No. What if horde and alliance like they are don't matter as much in the lore, and while players still pick them many races now consider themselves something else or just an affiliate because the old "core membership" goes?
Did not the old horde change ones, and the old alliance of Lordaeron? One thing is certain, change will come. I can only talk about how I see things, what my opinion is on the events in the lore and what I would like to see. It is not for me to say, this wouldn't happen or would because I don't develop this game.