That strategy results in large populations where poverty is highly concentrated. This leads to those areas becoming breeding grounds for crime and hopelessness. Over and over again in the US, large scale projects have exhibited this pattern of failure.
That's not to say that building affordable housing shouldn't be a priority. Indeed it should. But it might make more sense to build lots of small scale housing, with a focus on building viable community spaces rather than large scale ghettoes.
Also, rent control should be more widespread, instead of relentlessly fought against. This way, the housing that's created will have a chance to remain affordable, instead of constantly being at risk of gentrification.