Disagree. Threaded programming is not that difficult. Design matters. If you are trying to back fit threads into legacy code that has a traditional process based model with massively shared data structures it can be a little ugly.

Most peoples problems come with being over clever with their per thread data/stack, priorities, affinities, attributes, etc..a simple threaded program with a couple of locks for shared data and a flat schedule is efficient and easy to understand on multi-core systems.

Event loops and aio are nice but they are not a superior standalone solution as evidenced by nodes use of libuv.