In most Western cultures, the value in a historic building or monument lies primarily in its authenticity. A replica, no matter how faithfull, isn't the "real thing" and therefore a priori of lesser value.
There are, however, other aspects of cultural significance which have to be accounted for including historical value/associations, scientific values, aesthetic considerations, and social importance.
The assessment of these, and identification of ways forward, is set out in a series of charters by groups such as ICOMOS (International Council on Monuments and Other Sites) as well as national policy frameworks. It is a well understood process in heritage management circles.
By way of example, the recent destruction of Macintosh's GSA - one of Scotland's most import modern buildings, and of truly international value - has led to a debate about whether reconstruction would be appropriate. I argue, as do others, that it is not his fabric but his design aesthetic which is principal importance and hence substantial reconstruction is entirely appropriate.
In the case of Notre Dame de Paris, we now know that the larger part of the historic fabric - including, if photographs are to be believed, much of the upper stone vaulting - has survived the roof fire. We are therefore talking about a (substantial) repair rather than a rebuilding.
How that is implemented remains to be seen. There is a general presumption in favour of accurate reinstatement using traditional techniques, although SPAB and other groups influenced by Ruskin and Morris tend to whitter on about "honest repair" and nod in the direction of modern materials. You will rightly guess that I am not a fan of that latter approach.
In considering these issues, set aside considerations over WW2 reconstruction. Those were different times, with different pressures. Conservation practice and philosophy has moved on significantly.
If anyone is particular interested then take a look at the Illustrated Burra Charter, by ICOMOS Australia, as it will serve as a general introduction. If you can get a look at the original version of BS7913 that is also interesting, although the current update is less compelling as it trimmed out much of the detail.