As a lifelong Seattle resident/employee (psq, eastlake, cap hill), minus a few year-ish expat stints, I'd say it is partially correct but not the whole picture. All this said, I like it here and have no plans to leave permanently.

1) bad stuff definitely exists

3rd/Pine, parts of SoDo, the couple blocks between Occidental Square and Kobe Terrace, Aurora between like 85th and 145th, and bits of Beacon/Columbian/Rainier, are all what I'd call legitimately unsettling/dangerous experiences for WASPs and I totally understand why places downtown are having issues.

2) bad stuff isn't new

I got mugged multiple times on free-ride-zone buses as a kid/teen, lost lots of bikes, etc etc. The police have always been worse than useless and nobody I knew, even upper-middle-class neighborhood-dwellers, bothered reporting petty property crime. The impact of homelessness on downtown quality of life has pretty much always been a thing; consider https://www.seattletimes.com/seattle-news/warning-seattles-f... (from 2012) - the free-zone buses were literal mobile drug dens after a certain hour or on certain routes, was pretty nuts.

Before the viaduct was torn down, it was effectively a miles-long open-air shelter. I actually wonder how much of the current tensions are attributable to having physically gotten rid of one of the more inherently accommodating structures in the area, driving that population more out into the open a few blocks uphill.

3) bad stuff is getting worse

No argument that things haven't accelerated throughout the pandemic, though. Having actually spent a lot of time wandering around outside in the international district in early 2020, I can say that the current trajectory absolutely didn't start around/after the summer unrest. Imo, that's a totally unjustified attempt at ideologically linking unrelated concepts. As mentioned, cops have been useless since forever. The pandemic and pandemic-related restrictions have engendered an enormous amount of economic instability that bureaucratic-focused measures like rent assistance and eviction moratoria often fail to meaningfully mitigate; those most in need of help are the ones who aren't getting it. I think the destabilizing economic impact of the pandemic on the populations most vulnerable to homelessness is systematically discounted by the smug suburbanites who really really really want to find a cause, any cause, that isn't rooted in housing/inequality issues. Much easier to blame defunding the police.

4) rate of increase appears proportional to amount of socioeconomic deprivation

My take is that the amount of badness tracks pretty closely with aggregate economic fucked-ness. I did a lot of volunteering at the Compass Center circa the 2008 economic crisis and saw the progression firsthand: expensive housing begets housing instability, which is often the first step on a long downwards slide towards being a naked screaming shit-flinger. One gets driven into an encampment and now one's proximate to drug sales and has a lot of free time - doesn't take the most detailed analysis of all time to see how things continue to slide. People talk about multiple "classes" of homeless - the real honest Americans temporarily down on their luck, vs. the insane drug addicts accosting randoms on the street. While those distinctions do exist, it's often ignored that the boundaries between them are pretty fragile and it is very easy to progress downhill; the actual crazies come from somewhere, and that somewhere is unfortunately frequently the cauldron of fucked-ness that is living without stable housing.

All this said, I live my daily life without worrying about it much or even encountering examples of visible homelessness. The region is increasingly segregated on the basis of economic class, so for your Amazon dev working from home in Magnolia or whatever the issue is largely academic.