Construction is in fact never done. If it's not data centers then it will be something else: high-rise residences, bridges, spaceports, oil refineries, whatever. People always want more stuff and we'll never hit a limit in our lifetimes. Skilled construction work is tough and occasionally dangerous but it pays pretty well.

https://mikeroweworks.org/

Speculation about science fiction automation scenarios is not a sound basis for public policy. Lots of things could happen in the future. We can't reasonably plan ahead for all possible contingencies.