Capitalism makes rural life untenable, and forces people into the cities in search of jobs that pay high enough to survive off of. This forces people of different ethnic and religious backgrounds into close proximity with one another, which leads to diversity which reactionaries see as the destruction of the traditional heterogeneous society. Cities are also highly polluted, easy to get sick in, and full of safety hazards. Capitalism creates poverty alongside urbanization, and poverty leads to addiction, mental illness, and crime (since poverty is criminalized under capitalism, and so is doing what you need to survive, like stealing food) which in turn leads to overpolicing, prison slavery, etc.. Reactionaries skip over the part where capitalism causes poverty, and assume the cities themselves cause crime. Along with their favorite scapegoats: immigrants and minorities. So I think there's a combination of economic, environmental, and cultural grievances one can have with cities. Some of these grievances are reactionary, and some are sincere displeasure with the inconveniences of urban life (the economic and environmental issues, mainly).