[Jtsummers]

I agree with you. I don't think either concurrency or parallelism have ever been necessary. In 2019 with Intcode, it was the simplest approach (use multiple threads, one per VM) for a couple days, but it was never actually necessary. You could do the same thing with purely sequential code, but you had to juggle the state of multiple running systems yourself then. Threads were much easier (or coroutines, go routines, processes, etc.; some concurrency system).

And by design, every problem is solvable on decade old computers in a reasonable amount of time (seconds) so parallelism is great if you're looking to minimize the runtime, but it's never necessary.