I can only note that the past is beautiful because one never realises an emotion at the time. It expands later, and thus we don't have complete emotions about the present, only about the past.
Beauty is an experience, nothing else. It is not a fixed pattern or an arrangement of features. It is something felt, a glow or a communicated sense of fineness.
The fact is, the public make use of the classics of a country as a means of checking the progress of Art. They degrade the classics into authorities. They use them as bludgeons for preventing the free expression of Beauty in new forms.
Beauty is the mark God sets on virtue. Every natural action is graceful; every heroic act is also decent, and causes the place and the bystanders to shine.