The proper question is, when did threads stop being some kind of inscrutable black magic?

And the answer is, if you consider the whole of the programming space, that it's still a work in progress. There's a lot of good ideas in various places, but I'm not sure I've seen it unified into one coherent whole in any one language in such a way that it's simply a solved problem for virtually no effort. Every A-list or B-list language I know either has easy concurrency that can still get you deep in trouble (like Go), or "solves" the concurrency problem but at a fairly steep cost to the programmer (like Haskell).

Arguably Pony is the closest I've seen, but that's not even B-list yet, that's an "up and comer".

It's not, but it's needlessly complicated for what most people need to use threads for - async background tasks like fetching a resource or (as mentioned in the article) parsing RSS off the main thread.

I've done threads in the past, but for a good while now I've not had to do much thinking about async code thanks to advancements.

As domeone coming straight out of college, I disagree with your premise that threading is not accessible anymore. However, one possibility is that a proliferation of new languages brought with them new threading models and runtimes that all behave slightly differently. This makes many of the models look foreign.