I used to think that moral decay and the factors you mentioned brought down Imperial Rome.
While there were multiple factors that contributed to it's downfall it's speculated that they could still have been weathered had there not been corruption or incompetence at organisational levels, as evidenced by the fact that others found ways to continue on while incorporating some of the things learnt from the Romans. It could also have been that they'd grown too large for a centralised governance to understand how to respond to things happening on more local levels farther away, so it pretty much fell back to locals organising themselves. The Eastern Roman Empire faced similar problems, but still muddled on for nearly another 1000 years. At what scale, I'm not sure, I've not delved into it much.
With mention of Pompeii and Herculaneum I'm also reminded of the Minoan civilisation which seems to have mostly ended with a caldera on a similar scale to Krakatoa, if not bigger. Our earth can very easily humble us with hiccups and shudders like this when we think we're in control of everything.
I have yet to delve into Göbekli Tepe more, but my husband has listened to some bits on it and mentions it on occasion. He will readily admit to being a bit of a conspiracy nut, so loves to latch onto anything that might contradict the current narrative. 😉 I also find Sumer interesting as they seemed to have knowledge of the solar system that we only recently rediscovered. So that's another culture I'd like to look into further.
Regarding our supposed overpopulation, that's another interesting discussion topic. Our population today is certainly far above anything in recorded history and I do wonder if it could have been possible to sustain it without modern infrastructure. With lots of talk about population collapse because most countries have birth rates below replacement levels perhaps we are subconsciously self correcting. There are a lot of doomsayers who predict the extinction of the human race whether due to climate change, population collapse or self destruction, but I think history demonstrates that at least some always make it through.