> Can't you model any concurrent non-distributed system as a concurrent distributed system?

Yes, in the same way that you can give up `for` loops and `while` loops and `if` statements and `switch` statements and instead write them all with `goto`, but you don't do this, and anyone advising you to do this would be written off as insane. The entire thrust of this thread is that you can have a more reliable system that is easier to reason about if you use specific constructs that each have less power, and non-distributed systems have the option to do this. Unstructured concurrency should be reserved exclusively for contexts where structured concurrency is impossible, which is what the actor model is for.

You can certainly make any simple problem complicated enough to need a complex solution. But that’s just bad engineering.