Fish till ya drop.
Then suck it up
and fish the evening hatch.
The problem is the same all over Western Washington.
The ecology of cold water, freestone streams is NOT RICH.
When the salmon/steelhead were present in large numbers, a somewhat richer ecology existed due to the roe and rotting carcases.
But none of the freestone streams ever had a particularly rich ecology or rich nonanadromous fisheries.
Again, most of the "trout" caught in coastal and Puget Sound streams with access to salt water are not trout but parr and smolts of coho, steelhead and sea-run cutthroat. The best policy is to not fish for them. Concentrate on their adult brethren and don't use small trout flies, they are much less likely to hook and/or injure themselves on a size 4 Bulkley Mouse than on a size 16 Elk Hair Caddis.
Just like fishnfella said, the streams and rivers here and rich full of nutrients and there isn't a lot of food. I have found some streams in western washington where I will usually walk away with one or 2 13-14 inchers but it takes some exploring. Eastern Washington rivers are much more rich and the trout are much larger. Hope this helps,
There ARE larger fish above Snoqualmie Falls in all three forks (below Twin Falls on the South Fork) but you won't find them where the access is easy. Get away from the crowds and the easy to get to holes and you'll find bigger fish. There are steelhead, sea run cutts, and big dollies in the anadramous rivers but again, you have to pay your dues and do a little exploring.