“The interest in the heritage of specific locations and artefacts becomes more diluted not only with the passage of time but also with ever diminishing number of people associated with the purpose of each building or factory in its heyday.”
This is a key sentence. What is of importance to us now may well be of little or no interest to our descendants. It may be of little interest now to younger people for whom the artefact or building means nothing. Since we cannot preserve everything the judgement of the value of something for preservation is highly subjective. I stand to be corrected but I suspect we have one of the most vigorous arrangements for the preservation of objects and buildings in the world.