There are many varieties of apple that will grown marvelously in the PNW without any spraying. I used to acquire only know resistant varieties, but I hardly concern myself with that aspect anymore. I now choose almost exclusively by fruit quality. I picked Honeycrisp, Fuji, Goldrush, Cameo and Queen Cox purely for perceived fruit quality. No disease problems on any of them and no spraying. So far, so good.
However, you must find a way to defeat the dreaded Coddling Moth. That's the real challenge.

For wormy, you're going to have to deal with coddling moth. There are a lot of conversations here about that. The most promising sounding is "Surround" coated footies. Surround is an organic product. I'd search for footies here and see what comes up.

I'm not experienced enough to know if other disease problems are a big issue here in the northwest, but I've heard Coddling Moth and I think scab are the biggest issues.

By the way, I love that Twain quote.

You are very fortunate to have an old apple orchard. Disease will be the least of your worries.
Gradually prune and clean up the old trees and orchard. Mine has taken many years. Because of so many wild trees nearby you will find coddling moth and apple maggot to be to be your greatest threat. Even with sprays I lost almost everything to the apple maggot last summer. Constant rain kept everything washed off. The coddling moth will sometimes leave some good flesh but the maggots completely riddle and pulp the flesh. The footies and bags are a good way to go but labor intensive. I am east of you and a little colder but still on the coast. Plums seem to have less problems.