What matters is the complexity of the systems built out of these things. Threading primitives are simpler to understand in isolation, but lead to non-determinis

What matters is the complexity of the systems built out of these things. Threading primitives are simpler to understand in isolation, but lead to non-deterministic behavior. I've only used optics in a couple small situations, but even if I find some big downside, I'll still be open to "exotic immutable approaches".