How easy is the machinery and tools needed to keep all the infrastructure running? Earth movers are pretty maintainable and barely depreciate. Survey tools though? They have gotten famcy right? Water management has gone quite high tech in some ways. I could see them falling apart kind of like when some hospitals had to revert to paper tape logs. It didn't scale anymore.

> Earth movers are pretty maintainable and barely depreciate

Beware hardware DRM locking up the repairs. That would make everything more fragile.

The infra today is internet and semiconductors which run it, as well as global shipping without each we end up without even necessities.

Exactly. Building roads and aqueducts were empire-level knowledge skills in Ancient Rome, performed by the army legions. Thankfully they're highly localized skills today.