Here's one thing OP might be talking about – the "skyscraper district" of PDX practically emptied out during COVID, precisely because Portland has highly segregated big-B-business and residential districts. The rise of WFH meant that the whole district nearly emptied out overnight – especially anchor tenants like law firms and tech that were most amenable to WFH. Without any residential population in the area, boom: no place for a downtown flagship office.
Since I don't want to stealth-edit my post, another one was the rise of "nuisance homelessness" – the same shelter-in-place order prevented the City from sweeping people into warehouse shelters (but lower-capacity motel shelters were set up); and a combo drug-decriminalization-and-treatment-funding bill gave us the decriminalization but never actually funded the treatment in time, and so there was a lot of open-air drug use. That didn't help the return to "downtown" either.
Yes my company (small startup) closed its Portland office during COVID. It was opened for people who didn't want to be in the bay area. Pre COVID it was en vogue for bay area startups to have a PDX office. Then COVID happened and downtown became a ghost town.
I knew the end was in sight when it became company policy that no employee stay past 6PM without HR approval due to the danger.
Do you think east of the Willamette will be where any tech scene rebuilding might end up? I wonder which neighborhood might have the right mix of housing, office space, and recreation (ie food.)