Why are ancient buildings still standing 1500+ years later, but some buildings built like 30 years ago are falling apart?

Question

Why are ancient buildings still standing 1500+ years later, but some buildings built like 30 years ago are falling apart?

In: Other

Answer 1

Survival bias. Only a tiny fraction of buildings from 1500 ago survive. And those that so, survive because they were either forgotten and hidden, or actually used and cared for.