The original design is not the cathedral that stood there before the fire. People have been adding modern touches to the cathedral for centuries, why not continue that tradition?
2) Even with that, Viollet-Le-Duc is somewhat criticized for it's restoration works as he generally chose what looked "nice" as opposed to historical accuracy or significance.
Rebuilding the spire in a modern style would be a mistake in my opinion, or at the very least, a huge risk of style disunity of the building, rebuilding in Gothic style maybe boring but it's safe.
As to which technics could be used, that's another matter. Notre-Dame would not be the first cathedral to be rebuilt using the technics of the day.
Reims was rebuilt using concret, and the result is actually quite beautiful:
https://img.aws.la-croix.com/2019/04/17/1301016385/charpente...
Others were rebuilt using steel, Metz Cathedral for example.
I don't buy this idea. The original design was so beautiful that it inspired pilgrims for hundreds of years to make a trek to see it. Modern architecture is bland, glass-and-metal, uninspired crap; shiny jewels with no staying power that will be torn down within a century to make room for something else, or brutalist monstrosities put here to punish us with their brooding ugliness.