Any fish left alone to spawn in the wild, rear in the wild, and return to repeat the process will over time evolve to be WILD. They will adapt to the system as it exists today. But, keep putting in hatchery genes that are adapted to a different rearing environment and you get mongrel progeny.

It is true that the original, un-mixed natural stock probably doesn't exist. Unless one holds to extreme racial purity beliefs that doesn't matter if we let what surveys to spawn from the wild is allowed to spawn in the wild without genetic pollution from the hatchery fish.

Besides, the environment had changed over 200 years (hatcheries being more like 120 years old in the PNW) that something genetically pure from 200 years ago wouldn't make it today.