Seattle is building more apartments than just about anywhere, and now 1 in 10 units across the city are sitting empty. Landlords have responded by lowering rents slightly and offering more perks to get tenants in the door.
Generally unless we engage on a massive social housing project - which I am all for! - new construction is not the route to providing housing for poor people and it is dumb that people think it is. All new construction is "luxury housing" according to the advertisements and granite countertops don't cost much. In expensive places it's the price of land that makes things expensive, and the only thing you can do from a policy perspective absent massive subsidies is allow people to build more and build more units on less land. This mostly means lower parking requirements and taller buildings, though taller buildings means like 6 stories not 60. Even in Philadelphia it's mostly illegal to build Philadelphia (the zoning here has improved, but not the zoning process... it's complicated). Parking makes people crazy, but those cars take up a lot of space.
Also even here in Philadelphia we get a lot of "gentrification" conversation which is mostly stupid. Yes involuntary displacement of families is bad but very little of that is actually happening and you can still buy a nice house near transit for a hundred grand. Some people can't afford that, but that's because they are poor not because housing is expensive. A hundred grand is about as low as you can get for a family sized new construction unit even if land is free.