In fairness, concurrent data structures generally don’t represent what gp is talking about. Yes, very, very difficult to write a solid concurrent ring buffer. Writing Java’s concurrent hashmap - hard. Using it to implement a simple in memory kv store: not that hard.

But ensuring some parallelism while maintaining thread safety is straightforward in many contexts - an uncontended mutex is close to zero overhead. Languages like Rust make it harder to struggle with some of the thornier issues (data races which cannot be simulated by stepping threads).

E.g. in Java a typical system looks like a thread per request with some shared underlying data structures like caches or connection pools. Relatively easy to use these safely, or to guard some shared object with a synchronized.

Likewise with parallelism - a lot of problems just boil down to ‘do a few map reduces’ and the parallelism is pretty trivial.

Obviously, concurrent systems are fiendish to reason through - but there are a lot of cases where the complexity can be side stepped. Doesn’t seem to stop people writing scary code on the daily though.