Which is a long way of saying "You think it has low value as it stands, and high value as something else, but you don't have the wallet to buy it from the guys currently holding it" which is a long way of saying "People's tastes differ and you're in the minority".

But if you really think about it most nice monuments visited by tourists in any city, like churches, temples are actually buildinga mostly well restored and currently used in some way.

Colosseum is just a bunch of ugly ruins. Visiting Colosseum was one the most underwhelming experience of my life and I've travelled quite a bit. just build something nice Instead

Wow. You might want to check history again, or you have a very broad(to the point of meaningless) definition of civilisation.

Anyway, some other point: I for one enjoy certain old ruins much more, than most modern buildings. And even though I would like to see them in their former glory, I know that in most cases this would be increadibly hard, or just impossible, unless you just want a cheap movie requisite.