An issue with Portland Union as a passenger train station--at least one in the 2020's, and not the 1920's--is the ground-level boarding. It should be unacceptable
now, with the current level of services; it would be basically unusable if it were to function as a major train station a la anything in a medium-sized European or Asian city.
However, my understanding--gleaned from somewhere, I promise, if not the
Prosper Portland pdf I'd thought it was from (still worth a look-through; lots of info)--is that level boarding wouldn't provide the clearance freight trains need. Automated gap-fillers are fairly common in Europe, where mixed platform heights are the norm, but AFAIK don't exist anywhere in the U.S.
The higher frequencies between Portland and Seattle
proposed by WSDOT would seem much more feasible and pleasant if people didn't have to climb up into the rail cars as they do now.
I wish the few American cities with modern-ish rail service levels and modernized stations would see rail investment as the major economic breadbasket that it can be. There is
no major global city whose physical construction is benefitted by a dominion of highways through their middle; the opposite is pretty obviously true of rail.