All structures are worth preserving. The article is about a latrine. Do you think ancient Romans thought a literal shithole was worth preserving? And yet, it is now an important piece of history.

As for beauty, you never know, take the Eiffel tower for instance, when it was built, people found it ugly, and it was to be a temporary structure. Now it is the symbol of Paris, more popular than the Paris Pantheon, which much better fits the classical standards of beauty.

The Eiffel tower is also more historically significant, more representative of its time. The Paris Pantheon, is an imitation of the Roman style, beautiful, but probably not as interesting for future historians. If both building survive that is, which won't happen without continuous maintenance, at least for the Eiffel tower.

There are some structures worth preserving. Sagrada Família is one. Places of worship and private homes (at least those individually architect designed vs standard designs) tend to be a lot nicer than office blocks and other commercial places.

I do think a lot of new building hideous. Looking at St Paul's in London from the west so you see the hideous backdrop to its east is depressing.

Sand used to make concrete is a finite ressource, and extremely polluting to extract. Why wouldn't we save it and build lasting buildings?

Sydney Opera house comes to mind as something that might still be curious to people in 1000 years.

What makes you think buildings aren't going to change within the next 2000 years? Hell just look at all of the Tudor buildings dotted around. They probably didn't think they were anything special 600 years ago