The article makes some pretty good points here, density is important for public transit and large amounts of housing with medium amounts of affordable housing built can indeed end up with more than just small amounts of affordable only.

The gentrification topic however I think is an especially important point to make. Lack of building help cause gentrification because the rich people moving in after college getting a fancy job need places to live too, and if they don't have new houses then they'll just take from the available stock. i.e. the houses that poorer people are living in. They move to those neighborhoods and price everyone out because they don't have anywhere else absorbing them.

One point I do wish was covered more is how housing helps protect against homelessness. What the homeless need is homes to live in, and there's a strong correlation between available housing and homelessness rates.