I'm an atheist, but for me Notre Dame completely transcends religion. It's a hugely significant cultural and historical artifact that's extremely important to a lot of people, and it really hurt to see it burn. I've seen it from the outside several times but never went inside. It's an active church, and when I was there services were underway so I didn't want to just walk around snapping pictures. Now I'm sorry I never went in.
I had no idea there was so much wood in that roof structure. Hopefully it won't be rebuilt that way, or some future generation will have to watch it burn all over again. I'm not a structural or civil engineer, but it seems to me that steel could be used to support the roof, and it would be just as hidden as the wood that burned.
I was also surprised to learn that the roof was lead. I knew from our trips to Istanbul that lead is used to roof minarets in mosques, at least in that part of the world. I remember seeing large rolls of lead sheeting being used in a renovation and was surprised that would still be allowed today. I guess the same practice was followed for large Christian churches in Europe. I can only wonder where all that lead is right now. Quite a lot of it is probably in the river, with much more deposited as dust all over Paris downwind of the site. I'm sure a suitable replacement material can be found that has the same appearance.
But rebuilding the structure is probably the easy part. It's all the stuff inside. At least much of it seems to have survived, especially the small artifacts that could be quickly removed. By all accounts that was a heroic effort. But there was probably a lot of smoke and water damage throughout the interior. Sigh. Terrible.