Many good points here, there are a lot of factors we will never be able to pin down. The other species of salmon seldom fail in the same year, but there are huge fluctuations in run strength. Kings have been on the short end of the stick consistently, as they are in the most demand by sport fishers. We used to blame Asian offshore nets for intercepting the runs, then we blamed the commercial guys for intercepting the fish, and of course we always blame set netters along the shore around the rivers for intercepting the fish... They blame sport fishermen and catch and release
Here, the herring numbers have been down since the Exxon spill. Historically we go through cycles of overfishing, for the past 100 years, long before refrigeration existed on ships. The halibut stocks were almost wiped out in the 1800's in South central Alaska by PNW fleets, but rebounded when the overfishing stopped. We are in another slump with halibut stocks currently, locals tend to blame the charter boats that take 60% of the sport caught halibut annually. The fish are probably still there, but sport boats can't fish the deeper waters long lines do.
All we see to fix the issue is bag limit changes, closures, and size restrictions on the fish. None of those seem to change the dynamic quickly enough for us to see an improvement. Lots of issues, very few answers... Climate change is warming the water and other species are moving North preying on food stocks the salmon depend on.
Get out there and enjoy what you can while you can! As much as we would like the world to stay static to our memories of how "it should be/used to be" that's not going to happen.