My experience is mostly with the car-oriented city I live in; I can't speak as much to what it might look like elsewhere.
I do not think this is all NIMBYism, as I think some reasons are valid. it is also true that you cannot add a lot of population to some places without changing its character, and I do personally like living somewhere where I get recognised in local shops and third spaces and people say hello and/or smile at you on the streets quite often.
As to change, that happens when demand to live somewhere changes, one way or another. See my other comment where I discuss an increase in the demand:
With regard to the environmental impact, I was not thinking about climate change but things such as endangering habitats of rare species.