It's tragic, but "historic" disasters are the untold places of the world that have been completely lost to history.
We've had hundreds of years to document and preserve Notre Dame, and the structure itself remains intact, if damaged. We know exactly how it was made, and how it can be restored.
It's always unfortunate when natural events destroy sites of historical significance, but we're a lot better equipped than our ancestors to make sure their existence is never truly lost.
A dark day for sure, but not the end for this historic structure.