This isn't a statement against your other critiques of Seattle's government. In fact, I have no standing to speak on them given I've never been to the city.
But I'm be quite weary of criticisms against city's handling of their homeless populations, given the issue is a box of hand grenades, all with different timing mechanisms that must be diffused the moment it's opened.
The most vocal political actors around the issue are generally highly empathetic activists averse to almost any form of outcome oriented case management, metric collection or conditional aid policies; and those that vociferously oppose all forms of state-driven social aid.
Cities that pander to the first, compassion-oriented constituency tend to risk becoming a dumping ground for the region's less compassionate actors, and cities that pander to the other tend to dump their homeless populations on the more compassionate ones. This means that whoever tries to solve the issue first inevitably finds their public/private resources strained beyond reason.
Attempts to reconcile the two perspectives usually satisfy no one, and more often than not seem to produce counterproductive and Byzantine bureacratic mazes that ultimately produce little to no positive outcomes and lack the flexibility to adapt their social services on a case by case basis.