There is nothing kneejerking about being against 'fast fashion'.
The fashion industry is the second-largest consumer of the world's water supply. [0]
The fashion industry produces 10% of all humanity’s carbon emissions. [0]
For comparison it produces more carbon than international flights and maritime shipping combined. [0]
The wastefulness of it all is even more dismaying. 85% of the world's textile production ends in a landfill every year.[0]
I agree that all the things in your list are as non-essential as the fashion industry but none of them (except maybe for the meat industry) have the business volume and carbon impact of the fashion industry as it currently operates. None of this is sustainable.
[0] https://www.businessinsider.nl/fast-fashion-environmental-im...
Its just a manifestation of human need to be in a hierachy. Makes no sense to me to attack a particular symptom.
I can think of a lots examples more destructive than fashion
expensive cars
single family homes with 5 bedrooms and 4 toilets
yatches
driving/flying vacations
suburbs/ need for "space"
overeating meat
I think its a common kneejerk reaction against fashion in nerd circles because we never found it useful and something that played to our negatives. A complait that has very little to do with the environment, really.