Honestly that's a great tweet. In America, the way cities are built is horrible. Half of them are captured by existing land owners and can't change anything, and the other half are a totally subject to the whims of developers. Car hell is everywhere. Meanwhile urban population is generally growing.
When there are more people in your city, they need more places to live. When your city's infrastructure is bad, you need to do work to make it better. If there was a socialist party in power, hopefully we would be doing both.
Obviously we have capitalism now, and it's mostly true that there are enough houses to give everybody a place to live. But under the current system there is no mechanism to give those houses to those who need them. So if you're just trying to reduce harm right now, you still need to build more housing. Also, more co-ops or public housing would create more communities where general leftwing organization can happen.