Climates can change drastically across even just a few hundred years.

As I presently understand it, the initially fertile Nile-inundation that flooded the banks with precious crop-growing nutrients on a regular basis (for example in the time of Rameses II) slowed over the years, changing up certain equations upon many things. For example, once a jungle area slowly shifted to a desert area... that was arguably one of the long-form primary causes for the collapse of the once-mighty Egyptian Empire, after some thousands of years of primacy.

(later counterpart of sorts-- The Mayan Empire?)

And yet the Egyptian Empire was monumentally impressive in its prime, I would argue.

Gold leaf technique has been around for ~8000 years. The peak could have been gilded limestone.

Just because people will imagine that it's a solid block of gold at the top, which it obviously could not have been.

Yes, the pyramidion would almost certainly have been composed of an alloy, as I understand it. Quite possibly of silver, and other likely metals.

The Egyptian climate has been basically the same for the last 5000 years so the idea of desertification causing their downfall is inaccurate.

I'm not sure where I picked that up. Some literature, perhaps.

How would you better-phrase the situation?

I wouldn't make the claim that Egypt died to climate change.

There were roughly 2 peaks of Egyptian history, 3500BC (Old Kingdom under Khufu) and in 1500BC (New Kingdom). The fall of Egypt was climate based - Egypt provided much of the wheat for the Mediterranean and there wasn't a forced shortage before the fall of the empire.

Egypt collapsed due to poor leadership and Roman invasion.

The fall of Egypt was climate based

I mean...

Also incest. I would argue that was the cause of a lot of the poor leadership - the later pharaohs were inbred, brothers and sisters marrying. Genetic disaster.