Yes, exactly? That's what makes it easier.
Software engineering has been a thing for, if you squint, 70 years? Comparing that to thousands of years of humans trying to pile up rocks in various ways to make houses is unserious.
Moreover, there are only so many rocks you can pile up on top of each other. Software can be infinitely complex.
How often is the civil engineer asked to add major features to his 80% finished pile of rocks? Or to move the whole pile by 50m? How long is he expected to continue feature development on it after it's been built?
> extremely high-quality very-serious civil engineering work, built over millenia
Translation: When randomly piled up rocks resulted in many dead humans we dutifully wrote down not to do that particular thing again. Repeat for a couple thousands of years and you get your very serious civil engineering work.