Evidence is evidence. After WMD (which totally took me in, btw, you too?) Claims that evidence is "just over there" and "here are multiple different people reporting they've spoken to someone who saw it." Count for zero. Maybe they always should have but there's not doubt this stuff happens anymore. We watched it. (Hopefully) in horror as it unfolded without us objecting.
OTOH, the evidence linking APT38 to North Korea is pretty compelling. For example, there is a bunch of evidence collected independently identifying individuals associated with APT38, and these people worked for the North Korean company Chosun Expo.
See https://www.justice.gov/opa/press-release/file/1092091/downl... for the evidence in depth.
For what it's worth, quite a few people were skeptical about the WMD "evidence" at the time, and even more cynics like myself figured that true or false, it was mostly an excuse for George W to Do Something(tm) after 9/11 and at the same time finish off the war his dad started.