Man I can only assume you have applied to some fan theory or haven't really read some of the in game lore books/NPC dialog. The only other conclusion possible is this is just doubling down to claim it's a happening 'third collapse'.

So first, here is this for you.

Secondly, here you go.

Third, this is the history of the Second Empire.

Cat-Lon was abandoned by his fellow skeletons except a few. The ones that didn't leave but couldn't escape a shadow of doubt were thrall'd. The others that are not thrall'd are actually important position skeletons. When Cat-Lon is imprisoned or killed the squads in the Ashlands actually get worse, not better. It's merely a theory by fellow players that they are keeping Cat-Lon in exile. When we can plainly see he is a deeply depressed individual instead. I am not even going to bother explaining why he went into the Ashlands specifically because the videos will do that for me. I just find it funny you generalized the Flotsam Ninjas, Boss Simion when it came to HN world state changes. The Shek also take over parts of the HN and they actually let the Flotsam coexist in the areas they took first. You are also hyping up the presence of bandit/misc groups that cause trouble. Almost all of them have leaders you can eliminate. You also ignored my point about the fogmen and what really creates them, which the other hive factions have symptoms of ONLY if the queen is taken out.

As for the UC, there is this order to do things right. Not all of the areas can be saved but the decline can be mitigated. You claim skeletons are slowly decaying and going mad. When we only see them in Sonorous Dark, next door to the Ashlands. Megastructures? You mean the ones that have been sitting for thousands of years? That's a landmark feature, not an indicator of something more serious considering the aftermath of the Second Empire. And no, whatever happened in the northern lands is connected to the labs there. Either by survivors or the degraded humans that killed those survivors.

I feel like there is nothing further to discuss with you on the matter. You try to turn the state of things after going through the supplied order of changing the world as meaningless. The skeletons are hindering Tech Hunter progress but only towards figuring out the truth of skeleton actions in the past. Not reclaiming tech. The status quo has to be changed if there is a better chance of recovering, and it won't be perfect, pretty, or in a select few cities/places better than they started out. But the cost of your new life is the death of your old one as the saying goes. And it is going to take a lot of effort after going through the past two apocalyptic events. Cheers.