There is opposition to it across the ideological spectrum, the right doesnt like it, because they feel people should do for themselves, parts of the left doesnt because of one of two reasons A) it doesnt provide an acceptable enough standard of living for those pushed into it B) it doesnt provide the 'comprehensive care' required to really help people (as seen from folks inside the homelessness industrial complex, which is to say, anyone with a vested interest in continuing the status quo).

In reality housing first solves a great many problems, and creates some others - but its better than anything else we're currently doing.