More affordable housing only solves a problem for those with moderate incomes. Evidence: every other city in the US that has cheaper housing but also still plenty of homeless. Free and low-cost mental health services are closer to the mark, but still far from a simple problem. Many homeless people have complex, multi-faceted problems. Many resist initial contact. Many have trouble with maintaining any kind of regular schedule for either medication or counseling. Funding that many therapists (not just head-counters) and ensuring their security is a challenge unto itself. Not a simple problem at all.
If there's one thing that makes Silicon Valley unpleasant to me, it's the "simple, just do X" hand-wave that so many there indulge in regarding every damn topic. I'm sure your job isn't so simple a child could do it. Why act like everybody else's is?