That statement is the equivalent of inserting “just” into technical advice, as in “It’s just code” or “Just scale out.” If it was that simple, the problem would have been solved.

Here’s the laundry list of things Seattle has tried and is trying: https://www.seattle.gov/homelessness, https://www.seattle.gov/homelessness/addressing-the-crisis

Note that homelessness is not a problem of the same scale as Seattle in many cities around the country, and around the world.

These cities have in turn some measures and initiatives that are proven solutions that reduces homelessness. Note that not all of them could work in Seattle, but some of them might.