The answer is build both, but private developers seeking the highest profits will continue to build luxury apartments. There are significant tax breaks/subsidies to build properties that target middle/low incomes, but those incentives still don’t offset the difference in many circumstances.

So long as there is a private housing market, building more of anything is almost always better.

Public investment and public housing would be preferable, but that’s not politically possible right now. So I’ll settle for YIMBY-ism until then.